Electronics

Electronics

          Electronics deals with that involve active electrical components such as vacuum tubes, transistors, diodes, and integrated circuits, and associated passive interconnection technologies. The  behavior of active components and their ability to control electron flows makes amplification of weak signals possible and electronics is widely used in, , and. The ability of electronic devices to act as makes digital information processing possible. Interconnection technologies such as, electronics packaging technology, and other varied forms of communication infrastructure complete circuit functionality and transform the mixed components into a regular working system.

       Electronics is distinct from electrical and electromechanical science and technology, which deal with the generation, distribution, switching, storage, and conversion of electrical energy to and from other energy forms using wires, motors, generators, batteries, switches, relays, transformers, resistors and other passive components. This distinction started around 1906 with the invention by of the, which made electrical of weak radio signals and audio signals possible with a non-mechanical device. Until 1950 this field was called radio technology because its principal application was the design and theory of radio, and vacuum tubes.

Electronic devices and components

          An electronic component is any physical entity in an electronic system used to affect the electrons or their associated fields in a manner consistent with the intended function of the electronic system. Components are generally intended to be connected together, usually by being soldered to a, to create an electronic circuit with a particular function. Components may be packaged singly, or in more complex groups as integrated circuits. Some common electronic components are capacitors, inductors, resistors, diodes, transistors, etc. Components are often categorized as active.

Early electronic components

        Vacuum tubes were one of the earliest electronic components. They dominated electronics until the middle of the 1980s. Since that time, solid state devices have all but completely taken over. Vacuum tubes are still used in some specialist applications such as high power RF amplifiers, cathode ray tubes specialist audio equipment, guitar amplifiers and some microwave devices.

Types of circuits

Circuits and components can be divided into two groups, analog and digital. A particular device may consist of circuitry that has one or the other or a mix of the two types. There are,

1.     Analog circuits

2.     Digital circuits

Analog circuits

Most analog electronic application, such as radio receivers, are constructed from combinations of a few types of basic circuits. Analog circuits use a continuous range of voltage as opposed to discrete levels as in digital circuits.

The number of different analog circuits so far devised is huge, especially because a circuit can be defined as anything from a single component, to systems containing thousands of components.

Analog circuits are sometimes called linear circuits although many non linear effects are used in analog circuits such as mixers, modulators, etc. Good examples of analog circuits include vacuum tube and transistor amplifiers, operational amplifiers and oscillators.

One rarely finds modern circuits that are entirely analog. These days analog circuitry may use digital or even microprocessor techniques to improve performance. This type of circuit is usually called mixed signal rather than analog or digital.

Sometimes it may be difficult to differentiate between analog and digital circuits as they have elements of both linear and non linear operation. An example is the comparator which takes in a continuous range of voltage but only outputs one of two levels as in a digital circuit. Similarly, an overdrive transistor amplifier can take on the characteristics of a controlled having essentially two levels of output.

Digital circuits

          Digital circuits are electric circuits based on a number of discrete voltage levels. Digital circuits are the most common physical representation of Boolean algebra,, and are the basis of all digital computers. To most engineers, the terms digital circuit, digital system and logic are interchangeable in the context of digital circuits. Most digital circuits use a binary system with two voltage levels labeled 0 and 1. Often logic 0 will be a lower voltage and referred to as Low while logic 1 is referred to as High. However, some systems use the reverse definition or are current based. logic has been studied, and some prototype computers made. Computer, electronic clocks, and programmable logic controllers are constructed of  circuits. Digital signal processors are another example.

Heat dissipation and thermal management

Heat generated by electronic circuitry must be dissipated to prevent immediate failure and improve long term reliability. Techniques for heat dissipation can include and for air cooling and other forms of such as. These techniques use, of heat energy.

Noise

Electronic noise is defined as unwanted disturbances superposed on a useful signal that tend to obscure its information content. Noise is not the same as signal distortion caused by a circuit. Noise is associated with all electronic circuits. Noise may be electromagnetically or thermally generated, which can be decreased by lowering the circuit. Other types of noise, such as cannot be removed as they are due to limitations in physical properties.

Electronics theory

Mathematical methods are integral to the study of electronics. To become proficient in electronics it is also necessary to become proficient in the mathematics of circuit analysis.

Circuit analysis is the study of methods of solving generally linear systems for unknown variables such as the voltage at a certain or the current through a certain branch of a network. A common analytical tool for this is the circuit simulator. Also important to electronics is the study and understanding of theory.

Electronics lab

Due to the nature of electronics theory, laboratory experimentation is an important part of the study of electronics. These experiments are used to prove, verify, and reinforce laws and such as Ohm’s law etc. Historically, electronics labs have consisted of electronics devices and equipment located in a physical space, although in more recent years the trend has been towards electronics lab simulation software, such as, Circutlogix, multisim and Pspice.

Computer aided design

Today electronics engineers have the ability to using premanufactured building blocks such as, and. software programs include programs and design programs. Popular names in the EDA software world are NI Multisim, Cadence, PCB and Schematic, Mentor, Altium, LabCentre Electronics, gEDA, KiCad and many others.

Construction methods

Many different methods of connecting components have been used over the years. For instance, early electronics often used with components attached to wooden breadboards to construct circuits. Cord wood construction and wire wraps were other methods used. Most modern day electronics now use printed circuit boards made of materials such as, or the cheaper Synthetic Resin Bonded Paper, also known as Paxoline and characterized by its light yellow to brown colour. Health and environmental concerns associated with electronics assembly have gained increased attention in recent years, especially for products destined to the European Union.

Degradation

Rasberry crazy ants have been known to consume the insides of electrical wiring, and nest inside of electronics, they prefer DC to AC currents. This behavior is not well understood by scientists.

Electricity

Electricity is the set of physical phenomena associated with the presence and flow of. Electricity gives a wide variety of well-known effects, such as, lightning, static electricity, electromagnetic induction and electrical current. In addition, electricity permits the creation and reception of electromagnetic radiation such as radio waves.

 In electricity, charges produce electronic fields which act on other charges. Electricity occurs due to several types of physics,

         To understand electronics, you need to understand electricity and what it is. Basically, electricity is the flow of electrons due to a difference in electrical charge between two points. This difference in charge is created due to a difference in electron density. If you have a point where the electron density is higher than the electron density at another point, the electrons in the area of higher density will want to balance the charge by migrating towards the area with lower density. This migration is referred to as electrical current. Thus, flow in an electrical circuit is induced by putting more electrons on one side of the circuit than the other, forcing them to move through the circuit to balance the charge density.

Electric Charge: a property of some, which determines there. Electrically charged matter is influenced by, and produces, electromagnetic fields.

Electric Field: an especially simple type of electromagnetic field produced by an electric charge even when it is not moving. The electric field produces a force on other charges in its vicinity.

Electronic Potential: the capacity of an electric field to do on an, typically measured in amperes.

Electric Current: a movement or flow of electrically charged particles, typically measured in volts.

Electromagnets: Moving charges produce a. Electrical currents generate magnetic fields, and changing magnetic fields generate electrical currents.

In, electricity is used for,

Electric Power where electric current is used to energise equipment,

Electronics which deals with electrical circuits that involve active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies.

         Electrical phenomena have been studied since antiquity, though progress in theoretical understanding remained slow until the seventeenth and eighteenth centuries. Even then, practical applications for electricity were few, and it would not be until the late nineteenth century that were able to put it to industrial and residential use. The rapid expansion in electrical technology at this time transformed industry and society. Electricitys extraordinary versatility means it can be put to an almost limitless set of applications which include transport, heating, lightning, and communication. Electrical power is now the backbone of modern industrial society.

Electric charge

       The presence of charge gives rise to an electrostatic force: charges exert a on each other, an effect that was known, though not understood, in antiquity. A lightweight ball suspended from a string can be charged by touching it with a glass rod that has itself been charged by rubbing with a cloth. If a similar ball is charged by the same glass rod, it is found to repel the first, the charge acts to force the two balls apart. Two balls that are charged with a rubbed amber rod also repel each other. However, if one ball is charged by the glass rod, and the other by an amber rod, the two balls are found to attract each other. These phenomena were investigated in the late eighteenth century by, who deduced that charge manifests itself in two opposing forms. This discovery led to the well known axiom, like charged objects repel and opposite charged objects attract.

       The force acts on the charged particles themselves, hence charge has a tendency to spread itself as evenly as possible over a conducting surface. The magnitude of the electromagnetic force, whether attractive or repulsive, is given by, which relates the force to the product of the charges and has an relation to the distance between them. The electromagnetic force is very strong, second only in strength to the, but unlike that force it operates over all distances. In comparison with the much weaker, the electromagnetic force pushing two electrons apart is 10⁴² times that of the attraction pulling them together.

        Study has shown that the origin of charge is from certain types of which have the properties of electric charge. Electric charge gives rise to and interacts with the, one of the four of nature. The most familiar carriers of electrical charge are the electron and proton. Experiment has shown charge to be a, that is, the net charge within a will always remain constant regardless of any changes taking place within that system. Within the system, charge may be transferred between bodies, either by direct contact, or by passing along a conducting material, such as a wire. The informal term refers to the net presence of charge on a body, usually caused when dissimilar materials are rubbed together, transferring charge from one to the other.

The charge on electrons and protons is opposite in sign, hence an amount of charge may be expressed as being either negative or positive. By convention, the charge carried by electrons is deemed negative and that by protons positive, a custom that originated with the work of Benjamin Franklin. The amount of charge is usually given the symbol Q and expressed in, each electron carries the same charge of approximately −1.6022×10⁻¹⁹. The proton has a charge that is equal and opposite, and thus +1.6022×10⁻¹⁹ coulomb. Charge is possessed not just by, but also by, each bearing an equal and opposite charge to its corresponding particle.

Charge can be measured by a number of means, an early instrument being the, which although still in use for classroom demonstrations, has been superseded by the electronic electrometer.

In normal conditions all matter has a neutral or has a zero net charge. When an object receives an electron the object becomes negatively charged. When an object gives up an electron the object becomes positively charged. Each charge possesses electric field lines and charge quantities. A positive charge possesses charge quantities of +Q and has electric field lines going outward. A negative charge possesses charge quantities of -Q and has electric field lines going inward. In general, like charges will oppose each other and opposite charges will attract each other. Hence, it is a property of matter.

Electric current

       The movement of electric charge is known as an, the intensity of which is usually measured in amperes. Current can consist of any moving charged particles, most commonly these are electrons, but any charge in motion constitutes a current.

         By historical convention, a positive current is defined as having the same direction of flow as any positive charge it contains, or to flow from the most positive part of a circuit to the most negative part. Current defined in this manner is called. The motion of negatively charged electrons around an, one of the most familiar forms of current, is thus deemed positive in the opposite direction to that of the electrons. However, depending on the conditions, an electric current can consist of a flow of in either direction or even in both directions at once. The positive to negative convention is widely used to simplify this situation.

         The process by which electric current passes through a material is termed, and its nature varies with that of the charged particles and the material through which they are travelling. Examples of electric currents include metallic conduction, where electrons flow through such as metal, where flow through liquids, or through such as electrical sparks. While the particles themselves can move quite slowly, sometimes with an average only fractions of a millimeter per second, that drives them itself propagates at close to the, enabling electrical signals to pass rapidly along wires.

        Current causes several observable effects, which historically were the means of recognizing its presence. That water could be decomposed by the current from a voltaic pile was discovered by and in 1800, a process now known as electrolysis. Their work was greatly expanded upon by in 1833. Current through a causes localized heating, an effect studied mathematically in 1840. One of the most important discoveries relating to current was made accidentally by in 1820, when, while preparing a lecture, he witnessed the current in a wire disturbing the needle of a magnetic compass. He had discovered, a fundamental interaction between electricity and magnetic. The level of electromagnetic emissions generated by is high enough to produce, which can be detrimental to the workings of adjacent equipment.

           In engineering or household applications, current is often described as being either direct current or alternating current. These terms refer to how the current varies in time. Direct current, as produced by example from and required by most devices, is a unidirectional flow from the positive part of a circuit to the negative. If, as is most common, this flow is carried by electrons, they will be travelling in the opposite direction. Alternating current is any current that reverses direction repeatedly, almost always this takes the form of a sine wave. Alternating current thus pulses back and forth within a conductor without the charge moving any net distance over time. The time-averaged value of an alternating current is zero, but it delivers energy in first one direction, and then the reverse. Alternating current is affected by electrical properties that are not observed under direct current, such as and. These properties however can become important when circuitry is subjected to, such as when first energised.

Electric field

The concept of the electric was introduced by Michael Farady. An electric field is created by a charged body in the space that surrounds it, and results in a force exerted on any other charges placed within the field. The electric field acts between two charges in a similar manner to the way that the gravitational field acts between two, and like it, extends towards infinity and shows an inverse square relationship with distance. However, there is an important difference. Gravity always acts in attraction, drawing two masses together, while the electric field can result in either attraction or repulsion. Since large bodies such as planets generally carry no net charge, the electric field at a distance is usually zero. Thus gravity is the dominant force at distance in the universe, despite being much weaker.

         An electric field generally varies in space, and its strength at any one point is defined as the force that would be felt by a stationary, negligible charge if placed at that point. The conceptual charge, termed a, must be vanishingly small to prevent its own electric field disturbing the main field and must also be stationary to prevent the effect of as the electric field is defined in terms of, and force is a, so it follows that an electric field is also a vector, having both magnitude and direction. Specifically, it is a vector field.

            The study of electric fields created by stationary charges is called. The field may be visualised by a set of imaginary lines whose direction at any point is the same as that of the field. This concept was introduced by Faraday, whose term still sometimes sees use. The field lines are the paths that a point positive charge would seek to make as it was forced to move within the field, they are however an imaginary concept with no physical existence and the field permeates all the intervening space between the lines. Field lines emanating from stationary charges have several key properties, first, that they originate at positive charges and terminate at negative charges, second, that they must enter any good conductor at right angles, and third, that they may never cross nor close in on themselves.

A hollow conducting body carries all its charge on its outer surface. The field is therefore zero at all places inside the body. This is the operating principal of the, a conducting metal shell which isolates its interior from outside electrical effects.

         The principles of electrostatics are important when designing items of equipment. There is a finite limit to the electric field strength that may be withstood by any medium. Beyond this point, occurs and a causes flashover between the charged parts. Air, for example, tends to arc across small gaps at electric field strengths which exceed 30 kV per centimeter. Over larger gaps, its breakdown strength is weaker, perhaps 1 kV per centimeter. The most visible natural occurrence of this is, caused when charge becomes separated in the clouds by rising columns of air, and raises the electric field in the air to greater than it can withstand. The voltage of a large lightning cloud may be as high as 100 MV and have discharge energies as great as 250 kWh.

          The field strength is greatly affected by nearby conducting objects, and it is particularly intense when it is forced to curve around sharply pointed objects. This principle is exploited in the, the sharp spike of which acts to encourage the lightning stroke to develop there, rather than to the building it serves to protect.   

Electric potential

           The concept of electric potential is closely linked to that of the electric field. A small charge placed within an electric field experiences a force, and to have brought that charge to that point against the force requires. The electric potential at any point is defined as the energy required to bring a unit test charge from an slowly to that point. It is usually measured in, and one volt is the potential for which one of work must be expended to bring a charge of one from infinity. This definition of potential, while formal, has little practical application, and a more useful concept is that of, and is the energy required to move a unit charge between two specified points. An electric field has the special property that it is, which means that the path taken by the test charge is irrelevant: all paths between two specified points expend the same energy, and thus a unique value for potential difference may be stated. The volt is so strongly identified as the unit of choice for measurement and description of electric potential difference that the term sees greater everyday usage.

        For practical purposes, it is useful to define a common reference point to which potentials may be expressed and compared. While this could be at infinity, a much more useful reference is the itself, which is assumed to be at the same potential everywhere. This reference point naturally takes the name or ground. Earth is assumed to be an infinite source of equal amounts of positive and negative charge, and is therefore electrically uncharged and unchargeable.

           Electric potential is a, that is, it has only magnitude and not direction. It may be viewed as analogous to just as a released object will fall through a difference in heights caused by a gravitational field, so a charge will fall across the voltage caused by an electric field. As relief maps show marking points of equal height, a set of lines marking points of equal potential may be drawn around an electrostatically charged object. The equipotentials cross all lines of force at right angles. They must also lie parallel to a surface, otherwise this would produce a force that will move the charge carriers to even the potential of the surface.

        The electric field was formally defined as the force exerted per unit charge, but the concept of potential allows for a more useful and equivalent definition, the electric field is the local of the electric potential. Usually expressed in volts per meter, the vector direction of the field is the line of greatest slope of potential, and where the equipotentials lie closest together.

Electromagnets

          Orsted discovery in 1821 that a existed around all sides of a wire carrying an electric current indicated that there was a direct relationship between electricity and magnetism. Moreover, the interaction seemed different from gravitational and electrostatic forces, the two forces of nature then known. The force on the compass needle did not direct it to or away from the current carrying wire, but acted at right angles to it. orsted slightly obscure words were that the electric conflict acts in a revolving manner. The force also depended on the direction of the current, for if the flow was reversed, then the force did too.

              Orsted did not fully understand his discovery, but he observed the effect was reciprocal: a current exerts a force on a magnet, and a magnetic field exerts a force on a current. The phenomenon was further investigated by, who discovered that two parallel current carrying wires exerted a force upon each other: two wires conducting currents in the same direction are attracted to each other, while wires containing currents in opposite directions are forced apart. The interaction is mediated by the magnetic field each current produces and forms the basis for the international definition of the ampere.

         This relationship between magnetic fields and currents is extremely important, for it led to Michael Faraday's invention of the in 1821. Faraday's consisted of a sitting in a pool of mercury. A current was allowed through a wire suspended from a pivot above the magnet and dipped into the mercury. The magnet exerted a tangential force on the wire, making it circle around the magnet for as long as the current was maintained.

            Experimentation by Faraday in 1831 revealed that a wire moving perpendicular to a magnetic field developed a potential difference between its ends. Further analysis of this process, known as, enabled him to state the principle, now known as, that the potential difference induced in a closed circuit is proportional to the rate of change of through the loop. Exploitation of this discovery enabled him to invent the first in 1831, in which he converted the mechanical energy of a rotating copper disc to electrical energy. Faraday disc was inefficient and of no use as a practical generator, but it showed the possibility of generating electric power using magnetism, a possibility that would be taken up by those that followed on from his work.

Electric circuits

An electric circuit is an interconnection of electric components such that electric charge is made to flow along a closed path, usually to perform some useful task.

The components in an electric circuit can take many forms, which can include elements such as resistors, capacitors, switches, transformers and electronics. Electronic circuits active components usually semiconductors, and typically exhibit behaviour, requiring complex analysis. The simplest electric components are those that are termed passive and linear while they may temporarily store energy, they contain no sources of it, and exhibit linear responses to stimuli.

The resistors  is perhaps the simplest of passive circuit elements: as its name suggests, it the current through it, dissipating its energy as heat. The resistance is a consequence of the motion of charge through a conductor, in metals, for example, resistance is primarily due to collisions between electrons and ions. Ohm’s  is a basic law of, stating that the current passing through a resistance is directly proportional to the potential difference across it. The resistance of most materials is relatively constant over a range of temperatures and currents, materials under these conditions are known as ohmic. The, the unit of resistance, was named in honour of, and is symbolised by the Greek letter is the resistance that will produce a potential difference of one volt in response to a current of one amp.

The capacitor is a development of the Leyden jar and is a device that can store charge, and thereby storing electrical energy in the resulting field. It consists of two conducting plates separated by a thin layer, in practice, thin metal foils are coiled together, increasing the surface area per unit volume and therefore the. The unit of capacitance is the, named after, and given the symbol F one farad is the capacitance that develops a potential difference of one volt when it stores a charge of one coulomb. A capacitor connected to a voltage supply initially causes a current as it accumulates charge, this current will however decay in time as the capacitor fills, eventually falling to zero. A capacitor will therefore not permit a current, but instead blocks it.

The inductor is a conductor, usually a coil of wire, that stores energy in a magnetic field in response to the current through it. When the current changes, the magnetic field does too, a voltage between the ends of the conductor. The induced voltage is proportional to the of the current. The constant of proportionality is termed the. The unit of inductance is the, named after, a contemporary of Faraday. One Henry is the inductance that will induce a potential difference of one volt if the current through it changes at a rate of one ampere per second. The inductors behaviour is in some regards converse to that of the capacitor: it will freely allow an unchanging current, but opposes a rapidly changing one.

Electric power

       Electric power is the rate at which  is transferred by an electric circuit. The SI unit of is the Walt, one joule per second.

       Electric power, like, is the rate of doing, measured in, and represented by the letter P. The term wattage is used colloquially to mean electric power in watts. The electric power in produced by an electric current I consisting of a charge of Q coulombs every t seconds passing through an difference of V is

                 P = work done per unit time = QV = IV

                       t

                                               

where

Q is electric charge in

t is time in seconds

I is electric current in

V is electric potential or voltage in

            Electricity generation is often done with, but can also be supplied by chemical sources such as or by other means from a wide variety of sources of energy. Electric power is generally supplied to businesses and homes by the electric power industry. Electricity is usually sold by which the product of power in kilowatts is multiplied by running time in hours. Electric utilities measure power using, which keep a running total of the electric energy delivered to a customer.

Radio

Faraday's and Ampere’s work showed that a time varying magnetic field acted as a source of an electric field, and a time varying electric field was a source of a magnetic field. Thus, when either field is changing in time, then a field of the other is necessarily induced. Such a phenomenon has the properties of a, and is naturally referred to as an. Electromagnetic waves were analysed theoretically by James Clerk Maxwell in 1864. Maxwell developed a set of equations that could unambiguously describe the interrelationship between electric field, magnetic field, electric charge, and electric current. He could moreover prove that such a wave would necessarily travel at the, and thus light itself was a form of electromagnetic radiation, which unify light, fields, and charge are one of the great milestones of theoretical physics.

Thus, the work of many researchers enabled the use of electronics to convert signals into oscillating currents, and via suitably shaped conductors, electricity permits the transmission and reception of these signals via radio waves over very long distances.

Production and uses

Generation and transmission

Thales experiments with amber rods were the first studies into the production of electrical energy. While this method, now known as the, can lift light objects and generate sparks, it is extremely inefficient. It was not until the invention of the voltaic pile in the eighteenth century that a viable source of electricity became available. The voltaic pile, and its modern descendant, the, store energy chemically and make it available on demand in the form of electrical energy. The battery is a versatile and very common power source which is ideally suited to many applications, but its energy storage is finite, and once discharged it must be disposed of or recharged. For large electrical demands electrical energy must be generated and transmitted continuously over conductive transmission lines.

Electrical power is usually generated by electro mechanical driven by produced from combustion, or the heat released from nuclear reactions or from other sources such as extracted from wind or flowing water. The modern invented by in 1884 today generates about 80 percent of the in the world using a variety of heat sources. Such generators bear no resemblance to Faraday's homopolar disc generator of 1831, but they still rely on his electromagnetic principle that a conductor linking a changing magnetic field induces a potential difference across its ends. The invention in the late nineteenth century of the meant that electrical power could be transmitted more efficiently at a higher voltage but lower current. Efficient meant in turn that electricity could be generated at centralized, where it benefited from, and then be dispatched relatively long distances to where it was needed.

Since electrical energy cannot easily be stored in quantities large enough to meet demands on a national scale, at all times exactly as much must be produced as is required. This requires making careful predictions of their electrical loads, and maintaining constant co-ordination with their power stations. A certain amount of generation must always be held in to cushion an electrical grid against inevitable disturbances and losses.

Demand for electricity grows with great rapidity as a nation modernises and its economy develops. The United States showed a 12% increase in demand during each year of the first three decades of the twentieth century, a rate of growth that is now being experienced by emerging economies such as those of India or China. Historically, the growth rate for electricity demand has outstripped that for other forms of energy.

Environmental concerns with electricity generation have led to an increased focus on generation from, in particular from and. While debate can be expected to continue over the environmental impact of different means of electricity production, its final form is relatively clean.

Applications

Electricity is a very convenient way to transfer energy, and it has been adapted to a huge, and growing, number of uses. The invention of a practical in the 1870s led to becoming one of the first publicly available applications of electrical power. Although electrification brought with it its own dangers, replacing the naked flames of gas lighting greatly reduced fire hazards within homes and factories. Public utilities were set up in many cities targeting the burgeoning market for electrical lighting.

The joule heating effect employed in the light bulb also sees more direct use in electric heating. While this is versatile and controllable, it can be seen as wasteful, since most electrical generation has already required the production of heat at a power station. A number of countries, such as Denmark, have issued legislation restricting or banning the use of electric heating in new buildings. Electricity is however a highly practical energy source for, with representing a growing sector for electricity demand, the effects of which electricity utilities are increasingly obliged to accommodate.

Electricity is used within, and indeed the, demonstrated commercially in 1837 and, was one of its earliest applications. With the construction of first, and then, telegraph systems in the 1860s, electricity had enabled communications in minutes across the globe. Optical fiber and technology have taken a share of the market for communications systems, but electricity can be expected to remain an essential part of the process.

The effects of electromagnetism are most visibly employed in the, which provides a clean and efficient means of motive power. A stationary motor such as a is easily provided with a supply of power, but a motor that moves with its application, such as an, is obliged to either carry along a power source such as a battery, or to collect current from a sliding contact such as a pantograph.

Electronic devices make use of, perhaps one of the most important inventions of the twentieth century, and a fundamental building block of all modern circuitry. A modern may contain several billion miniaturized transistors in a region only a few centimeters square.

Electricity is also used to fuel public transportation, including electric buses and trains.

Electricity and the natural world

                  

        Physiological effects

                    A voltage applied to a human body causes an electric current through the tissues, and although the relationship is non linear, the greater the voltage, the greater the current. The threshold for perception varies with the supply frequency and with the path of the current, but is about 0.1 mA to 1 mA for mains frequency electricity, though a current as low as a microamp can be detected as an effect under certain conditions. If the current is sufficiently high, it will cause muscle contraction, of the heart, and. The lack of any visible sign that a conductor is electrified makes electricity a particular hazard. The pain caused by an electric shock can be intense, leading electricity at times to be employed as a method of torture. Death caused by an electric shock is referred to as electrocution. Electrocution is still the means of in some jurisdictions, though its use has become rarer in recent times

Electrical phenomena in nature

Electricity is not a human invention, and may be observed in several forms in nature, a prominent manifestation of which is lightning. Many interactions familiar at the macroscopic level, such as touch, friction or chemical bonding, are due to interactions between electric fields on the atomic scale. The is thought to arise from a natural dynamo of circulating currents in the planet's core. Certain crystals, such as, or even, generate a potential difference across their faces when subjected to external pressure. This phenomenon is known as, from the Piezein, meaning to press, and was discovered in 1880 by Pierre and Jacques Curie . The effect is reciprocal, and when a piezoelectric material is subjected to an electric field, a small change in physical dimensions takes place.

Some organisms, such as, are able to detect and respond to changes in electric fields, an ability known as, while others, termed, are able to generate voltages themselves to serve as a predatory or defensive weapon. The order, of which the best known example is the, detect or stun their prey via high voltages generated from modified muscle cells called. All animals transmit information along their cell membranes with voltage pulses called, whose functions include communication by the nervous system between and neurons and muscles. An electric shock stimulates this system, and causes muscles to contract. Action potentials are also responsible for coordinating activities in certain plants.

Cultural perception

In the 19th and early 20th century, electricity was not part of the everyday life of many people, even in the industrialized western world. The popular cultural of the time accordingly often depicts it as a mysterious, quasi magical force that can slay the living, revive the dead or otherwise bend the laws of nature. This attitude began with the 1771 experiments of in which the legs of dead frogs were shown to twitch on application of. Revitalization or resuscitation of apparently dead or drowned persons was reported in the medical literature shortly after Galvani's work. These results were known to when she authored, although she does not name the method of revitalization of the monster. The revitalization of monsters with electricity later became a stock theme in horror films.

As the public familiarity with electricity as the lifeblood of the grew, its wielders were more often cast in a positive light, such as the workers who finger death at their gloves end as they piece and repiece the living wires in 1907 poem. Electrically powered vehicles of every sort featured large in adventure stories such as those of and the books. The masters of electricity, whether fictional or real including scientists such as, or were popularly conceived of as having wizard like powers.

With electricity ceasing to be a novelty and becoming a necessity of everyday life in the latter half of the 20th century, it required particular attention by popular culture only when it stops flowing, an event that usually signals disaster. The people who keep it flowing, such as the nameless hero of song, are still often cast as heroic, wizard like figures.

Basic Electronics

The goal of this chapter is to provide some basic information about electronic circuits. We make the assumption that you have no prior knowledge of electronics, electricity, or circuits, and start from the basics. This is an unconventional approach, so it may be interesting, or at least amusing, even if you do have some experience. So, the first question is a circuit is a structure that directs and controls electric currents, presumably to perform some useful function. The very name circuit implies that the structure is closed, something like a loop. That is all very well, but this answer immediately raises a new question, again, the name current indicates that it refers to some type of flow, and in this case we mean a flow of electric charge, which is usually just called charge because electric charge is really the only kind there is.

What is Charge

No one knows what charge really is anymore than anyone knows what gravity is. Both are models, constructions, fabrications if you like, to describe and represent something that can be measured in the real world, specifically a force. Gravity is the name for a force between masses that we can feel and measure. Early workers observed that bodies in certain electrical condition also exerted forces on one another that they could measure, and they invented charge to explain their observations. Amazingly, only three simple postulates or assumptions, plus some experimental observations, are necessary to explain all electrical phenomena. Everything: currents, electronics, radio waves, and light. Not many things are so simple, so it is worth stating the three postulates clearly.

Charge exists 

We just invent the name to represent the source of the physical force that can be observed. The assumption is that the more charge something has, the more force will be exerted. Charge is measured in units of Coulombs, abbreviated C. The unit was named to honor Charles Augustin Coulomb the French aristocrat and engineer who first measured the force between charged objects using a sensitive torsion balance he invented. Coulomb lived in a time of political unrest and new ideas, the age of Voltaire and Rousseau. Fortunately, Coulomb completed most of his work before the revolution and prudently left Paris with the storming of the Bastille.

Charge comes in two styles

We call the two styles positive charge, +, and negative charge, - . Charge also comes in lumps of, which is about two ten million trillionths of a Coulomb. The discrete nature of charge is not important for this discussion, but it does serve to indicate that a Coulomb is a LOT of charge.

Charge is conserved

You cannot create it and you cannot annihilate it. You can, however, neutralize it. Early workers observed experimentally that if they took equal amounts of positive and negative charge and combined them on some object, then that object neither exerted nor responded to electrical forces, effectively it had zero net charge. This experiment suggests that it might be possible to take uncharged, or neutral, material and to separate somehow the latent positive and negative charges. If you have ever rubbed a balloon on wool to make it stick to the wall, you have separated charges using mechanical action.

Those are the three postulates. Now we will present some of the experimental findings that both led to them and amplify their significance.

 Voltage   

          First we return to the basic assumption that forces are the result of charges. Specifically, bodies with opposite charges attract, they exert a force on each other pulling them together. The magnitude of the force is proportional to the product of the charge on each mass. This is just like gravity, where we use the term mass to represent the quality of bodies that results in the attractive force that pulls them together.

Electrical force, like gravity, also depends inversely on the distance squared between the two bodies; short separation means big forces. Thus it takes an opposing force to keep two charges of opposite sign apart, just like it takes force to keep an apple from falling to earth. It also takes work and the expenditure of energy to pull positive and negative charges apart, just like it takes work to raise a big mass against gravity, or to stretch a spring. This stored or potential energy can be recovered and put to work to do some useful task. A falling mass can raise a bucket of water, a retracting spring can pull a door shut or run a clock. It requires some imagination to devise ways one might hook on to charges of opposite sign to get some useful work done, but it should be possible. 

The potential that separated opposite charges have for doing work if they are released to fly together is called voltage, measured in units of volts. The greater the amount of charge and the greater the physical separation, the greater the voltage or stored energy. The greater the voltage, the greater the force that is driving the charges together. Voltage is always measured between two points, in this case, the positive and negative charges. If you want to compare the voltage of several charged bodies, the relative force driving the various charges, it makes sense to keep one point constant for the measurements. Traditionally, that common point is called ground.

 

They experience a force pushing them apart, and an opposing force is necessary to hold them together, like holding a compressed spring. Work can potentially be done by letting the charges fly apart, just like releasing the spring. Our analogy with gravity must end here: no one has observed negative mass, negative gravity or uncharged bodies flying apart unaided. Too bad, it would be a great way to launch a space probe. The voltage between two separated like charges is negative, they have already done their work by running apart, and it will take external energy and work to force them back together. 

So how do you tell if a particular bunch of charge is positive or negative. Even with two charges, you can only tell if they are the same or opposite. The names are relative, someone has to define which one is positive. Similarly, the voltage between two points A and B, V, is relative. If V_AB is positive you know the two points are oppositely charged, but you cannot tell if point A has positive charge and point B negative, or visa versa. However, if you make a second measurement between A and another point C, you can at least tell if B and C have the same charge by the relative sign of the two voltages, V_AB and V_AC to your common point A. You can even determine the voltage between B and C without measuring it, V_BC = V_AC - V_AB . This is the advantage of defining a common point, like A, as ground and making all voltage measurements with respect to it. If one further defines the charge at point A to be negative charge, then a positive V_AB means point B is positively charged, by definition. The names and the signs are all relative, and sometimes confusing if one forgets what the reference or ground point is.

Current   

Charge is mobile and can flow freely in certain materials, called conductors. Metals and a few other elements and compounds are conductors. Materials that charge cannot flow through are called insulators. Air, glass, most plastics, and rubber are insulators, for example. And then there are some materials called semiconductors that, historically, seemed to be good conductors sometimes but much less so other times. Silicon and germanium are two such materials. Today, we know that the difference in electrical behavior of different samples of these materials is due to extremely small amounts of impurities of different kinds, which could not be measured earlier. This recognition and the ability to precisely control the impurities has led to the massive semiconductor electronics industry and the near magical devices it produces, including those on your Robo Board. We will discuss semiconductor devices later, now let us return to conductors and charges. 

There is a force between them, the potential for work, and thus a voltage. Now we connect a conductor between them, a metal wire. On the positively charged sphere, positive charges rush along the wire to the other sphere, repelled by the nearby similar charges and attracted to the distant opposite charges. The same thing occurs on the other sphere and negative charge flows out on the wire. Positive and negative charges combine to neutralize each other, and the flow continues until there are no charge differences between any points of the entire connected system. There may be a net residual charge if the amounts of original positive and negative charge were not equal, but that charge will be distributed evenly so all the forces are balanced. If they were not, more charge would flow. The charge flow is driven by voltage or potential differences. After things have quieted down, there is no voltage difference between any two points of the system and no potential for work. All the work has been done by the moving charges heating up the wire.

The flow of charge is called electrical current. Current is measured in amperes, amps for short. An ampere is defined as a flow of one Coulomb of charge in one second past some point. While a Coulomb is a lot of charge to have in one place, an ampere is a common amount of current, about one ampere flows through a 100 watt incandescent light bulb, and a stove burner or a large motor would require ten or more amperes. On the other hand low power digital circuits use only a fraction of an ampere, and so we often use units of 1/1000 of an ampere, a milliamp, abbreviated as ma, and even 1/1000 of a milliamp, or a microamp. The currents on the Robo Board are generally in the milliamp range, except for the motors, which can require a full ampere under heavy load. Current has a direction, and we define a positive current from point A to B as the flow of positive charges in the same direction. Negative charges can flow as well, in fact, most current is actually the result of negative charges moving. Negative charges flowing from A to B would be a negative current, but, and here is the tricky part, negative charges flowing from B to A would represent a positive current from A to B. The net effect is the same, positive charges flowing to neutralize negative charge or negative charges flowing to neutralize positive charge, in both cases the voltage is reduced and by the same amount.

Batteries   

Charges can be separated by several means to produce a voltage. A battery uses a chemical reaction to produce energy and separate opposite sign charges onto its two terminals. As the charge is drawn off by an external circuit, doing work and finally returning to the opposite terminal, more chemicals in the battery react to restore the charge difference and the voltage. The particular type of chemical reaction used determines the voltage of the battery, but for most commercial batteries the voltage is about 1.5 V per chemical section or cell. Batteries with higher voltages really contain multiple cells inside connected together in series. Now you know why there are 3 V, 6 V, 9 V, and 12 V batteries, but no 4 or 7 V batteries. The current a battery can supply depends on the speed of the chemical reaction supplying charge, which in turn often depends on the physical size of the cell and the surface area of the electrodes. The size of a battery also limits the amount of chemical reactants stored. During use, the chemical reactants are depleted and eventually the voltage drops and the current stops. Even with no current flow, the chemical reaction proceeds at a very slow rate, so a battery has a finite storage or shelf life, about a year or two in most cases. In some types of batteries, like the ones we use for the robot, the chemical reaction is reversible, applying an external voltage and forcing a current through the battery, which requires work, reverses the chemical reaction and restores most, but not all, the chemical reactants. This cycle can be repeated many times. Batteries are specified in terms of their terminal voltage, the maximum current they can deliver, and the total current capacity in ampere-hours. 

You should handle batteries carefully, especially the ones we use in this course. Chemicals are a very efficient and compact way of storing energy. Just consider the power of gasoline or explosives, or the fact that you can play soccer for several hours powered only by a slice of cold pizza for breakfast. Never connect the terminals of a battery together with a wire or other good conductor. The battery we use for the Robo Board is similar to the battery in cars, which uses lead and sulphuric acid as reactants. Such batteries can deliver very large currents through a short circuit, hundreds of amperes. The large current will heat the wire and possibly burn you; the resulting rapid internal chemical reactions also produce heat and the battery can explode, spreading nasty, reactive chemicals about. Charging these batteries with too large a current can have the same effect. Double check the circuit and instructions before connecting a battery to any circuit.

Circuit Elements

Resistors   

       We need some way to control the flow of current from a voltage source, like a battery, so we do not melt wires and blow up batteries. If you think of current, charge flow, in terms of water flow, a good electrical conductor is like big water pipe. Water mains and fire hoses have their uses, but you do not want to take a drink from one. Rather, we use small pipes, valves, and other devices to limit water flow to practical levels. Resistors do the same for current, they resist the flow of charge, they are poor conductors. The value of a resistor is measured in ohms and represented by the Greek letter capital omega. There are many different ways to make a resistor. Some are just a coil of wire made of a material that is a poor conductor. The most common and inexpensive type is made from powdered carbon and a glue like binder. Such carbon composition resistors usually have a brown cylindrical body with a wire lead on each end, and colored bands that indicate the value of the resistor.

There are other types of resistors in your robot kit. The potentiometer is a variable resistor. When the knob of a potentiometer is turned, a slider moves along the resistance element. Potentiometers generally have three terminals, a common slider terminal, and one that exhibits increasing resistance and one that has decreasing resistance relative to the slider as the shaft is turned in one direction. The resistance between the two stationary contacts is, of course, fixed, and is the value specified for the potentiometer. The photo resistor or photocell is composed of a light sensitive material. When the photocell is exposed to more light, the resistance decreases. This type of resistor makes an excellent light sensor. 

Ohm's Law
 

Ohm's law describes the relationship between voltage, V , which is trying to force charge to flow, resistance, R , which is resisting that flow, and the actual resulting current I . The relationship is simple and very basic. Thus large voltages and/or low resistances produce large currents. Large resistors limit current to low values. Almost every circuit is more complicated than just a battery and a resistor, It refers to the voltage across the resistor, the voltage between the two terminal wires. Looked at another way that voltage is actually produced by the resistor. The resistor is restricting the flow of charge, slowing it down, and this creates a traffic jam on one side, forming an excess of charge with respect to the other side. Any such charge difference or separation results in a voltage between the two points, as explained above. Ohm's law tells us how to calculate that voltage if we know the resistor value and the current flow. This voltage drop is analogous to the drop in water pressure through a small pipe or small nozzle. 

 Power   

Current flowing through a poor conductor produces heat by an effect similar to mechanical friction. That heat represents energy that comes from the charge travelling across the voltage difference. Remember that separated charges have the potential to do work and provide energy. The work involved in heating a resistor is not very useful, unless we are making a hotplate; rather it is a by product of restricting the current flow. Power is measured in units of watts, named after James Watt, the Englishman who invented the steam engine, a device for producing lots of useful power. The power that is released into the resistor as heat can be calculated as P=VI , where I is the current flowing through the resistor and V is the voltage across it. Ohm's law relates these two quantities, so we can also calculate the power as the power produced in a resistor raises its temperature and can change its value or destroy it. Most resistors are air-cooled and they are made with different power handling capacity. The most common values are 1/8, 1/4, 1, and 2 watt resistors, and the bigger the wattage rating, the bigger the resistor physically. Some high power applications use special water cooled resistors. Most of the resistors on the Robo Board are 1/8 watt.

Combinations of Resistors   

          Resistors are often connected together in a circuit, so it is necessary to know how to determine the resistance of a combination of two or more resistors. There are two basic ways in which resistors can be connected, in series and in parallel. Determining the total resistance for two or more resistors in series is very simple. Total resistance equals the sum of the individual resistances. In this case, R_T=R₁+R2 . This makes common sense, if you think again in terms of water flow, a series of obstructions in a pipe add up to slow the flow more than any one. The resistance of a series combination is always greater than any of the individual resistors.

Our water pipe analogy indicates that it should be easier for current to flow through this multiplicity of paths, even easier than it would be to flow through any single path. Thus, we expect a parallel combination of resistors to have less resistance than any one of the resistors. Some of the total current will flow through R1 and some will flow through R2, causing an equal voltage drop across each resistor. More current, however, will flow through the path of least resistance. The formula for total resistance in a parallel circuit is more complex than for a series circuit.

RT={1{1R1}+{1R2}...+{1Rn}}

Parallel and series circuits can be combined to make more complex structures, but the resulting complex resistor circuits can be broken down and analyzed in terms of simple series or parallel circuits. There are several reasons; you might use a combination to get a value of resistance that you needed but did not have in a single resistor. Resistors have a maximum voltage rating, so a series of resistors might be used across a high voltage.

Capacitors   

         Capacitors are another element used to control the flow of charge in a circuit. The name derives from their capacity to store charge, rather like a small battery. Capacitors consist of two conducting surfaces separated by an insulator; a wire lead is connected to each surface. You can imagine a capacitor as two large metal plates separated by air, although in reality they usually consist of thin metal foils or films separated by plastic film or another solid insulator, and rolled up in a compact package.

           As soon as the connection is made charge flows from the battery terminals, along the wire and onto the plates, positive charge on one plate, negative charge on the other. The like sign charges on each terminal want to get away from each other. In addition to that repulsion, there is an attraction to the opposite sign charge on the other nearby plate. Initially the current is large, because in a sense the charges cannot tell immediately that the wire does not really go anywhere, that there is no complete circuit of wire. The initial current is limited by the resistance of the wires, or perhaps by a real resistor, as we have shown in Fig. But as charge builds up on the plates, charge repulsion resists the flow of more charge and the current is reduced. Eventually, the repulsive force from charge on the plate is strong enough to balance the force from charge on the battery terminal, and all current stops. Time for two different values of resistors. For a large resistor, the whole process is slowed because the current is less, but in the end, the same amount of charge must exist on the capacitor plates in both cases. The magnitude of the charge on each plate is equal.

The existence of the separated charges on the plates means there must be a voltage between the plates, and this voltage be equal to the battery voltage when all current stops. After all, since the points are connected by conductors, they should have the same voltage; even if there is a resistor in the circuit, there is no voltage across the resistor if the current is zero, according to Ohm's law. The amount of charge that collects on the plates to produce the voltage is a measure of the value of the capacitor, its capacitance, measured in farads. The relationship is C = Q/V, where Q is the charge in Coulombs. Large capacitors have plates with a large area to hold lots of charge, separated by a small distance, which implies a small voltage. A one farad capacitor is extremely large, and generally we deal with microfarads, one millionth of a farad, or picofarads, one trillionth (10^-12) of a farad. 

Consider the   circuit of Fig. again. Suppose we cut the wires after all current has stopped flowing. The charge on the plates is now trapped, so there is still a voltage between the terminal wires. The charged capacitor looks somewhat like a battery now. If we connected a resistor across it, current would flow as the positive and negative charges raced to neutralize each other. Unlike a battery, there is no mechanism to replace the charge on the plates removed by the current, so the voltage drops, the current drops, and finally there is no net charge left and no voltage differences anywhere in the circuit. The behavior in time of the current, the charge on the plates, and the voltage looks just like the graph in Fig. This curve is an exponential function, The RC time constant is a measure of how fast the circuit can respond to changes in conditions, such as attaching the battery across the uncharged capacitor or attaching a resistor across the charged capacitor. The voltage across a capacitor cannot change immediately, it takes time for the charge to flow, especially if a large resistor is opposing that flow. Thus, capacitors are used in a circuit to damp out rapid changes of voltage.

Combinations of Capacitors   

Like resistors, capacitors can be joined together in two basic ways: parallel and series. It should be obvious from the physical construction of capacitors that connecting two together in parallel results in a bigger capacitance value. A parallel connection results in bigger capacitor plate area, which means they can hold more charge for the same voltage. Thus, the formula for total capacitance in a parallel circuit is,

CT=C1+C2...+Cn ,

The same form of equation for resistors in series, which can be confusing unless you think about the physics of what is happening. 

The capacitance of a series connection is lower than any capacitor because for a given voltage across the entire group, there will be less charge on each plate. The total capacitance in a series circuit is

CT={1{1C1}+{1C2}...+{1Cn}}.

Again, this is easy to confuse with the formula for parallel resistors, but there is a nice symmetry here.

Inductors   

Inductors are the third and final type of basic circuit component. An inductor is a coil of wire with many windings, often wound around a core made of a magnetic material, like iron. The properties of inductors derive from a different type of force than the one we invented charge to explain, magnetic force rather than electric force. When current flows through a coil it produces a magnetic field in the space outside the wire, and the coil acts just like any natural, permanent magnet, attracting iron and other magnets. If you move a wire through a magnetic field, a current will be generated in the wire and will flow through the associated circuit. It takes energy to move the wire through the field, and that mechanical energy is transformed to electrical energy. This is how an electrical generator works. If the current through a coil is stopped, the magnetic field must also disappear, but it cannot do so immediately. The field represents stored energy and that energy must go somewhere. The field contracts toward the coil, and the effect of the field moving through the wire of the coil is the same as moving a wire through a stationary field, a current is generated in the coil. This induced current acts to keep the current flowing in the coil; the induced current opposes any change, an increase or a decrease, in the current through the inductor. Inductors are used in circuits to smooth the flow of current and prevent any rapid changes. 

The current in an inductor is analogous to the voltage across a capacitor. It takes time to change the voltage across a capacitor, and if you try, a large current flows initially. Similarly, it takes time to change the current through an inductor, and if you insist, say by opening a switch, a large voltage will be produced across the inductor as it tries to force current to flow. Such induced voltages can be very large and can damage other circuit components, so it is common to connect some element, like a resistor or even a capacitor across the inductor to provide a current path and absorb the induced voltage.

Inductors are measured in henrys, another very big unit, so you are more likely to see millineries, and micro henries. There are almost no inductors on the Robo Board, but you will be using some indirectly, the motors act like inductors in many ways. In a sense an electric motor is the opposite of an electrical generator. If current flows through a wire that is in a magnetic field, a mechanical force will be generated on the wire. That force can do work. In a motor, the wire that moves through the field and experiences the force is also in the form of a coil of wire, connected mechanically to the shaft of the motor. This coil looks like and acts like an inductor, if you turn off the current, the coil will still be moving through the magnetic field, and the motor now looks like a generator and can produce a large voltage. The resulting inductive voltage spike can damage components, such as the circuit that controls the motor current. In the past this effect destroyed a lot of motor controller chips and other Robo Board components. The present board design contains special diodes that will withstand and safely dissipate the induced voltage we hope.

Combinations of Inductors

You already know how inductors act in combination because they act just like resistors. Inductance adds in series. This makes physical sense because two coils of wire connected in series just looks like a longer coil. Parallel connection reduces inductance because the current is split between the several coils and the fields in each are thus weaker. 

Definition Electronics

The branch of physics and technology concerned with the design of circuits using transistors and microchips, and with the behavior and movement of electrons in a semiconductor, conductor, vacuum, or gas, electronics is seen as a growth industry electronics engineer. Circuits or devices using transistors, microchips, and other components, the electronics have been incorporated inside a connector.

Singular in construction a branch of physics that deals with the emission, behavior, and effects of electrons as in electron tubes and transistors and with electronic devices.

Branch of physics that deals with the emission, behavior, and effects of and with electronic devices. The beginnings of electronics can be traced to experiments with. In the 1880s and others observed the flow of current between elements in an evacuated glass tube. A two electrode constructed by John A. Fleming produced a useful output current. The invented by, was followed by further improvements. The invention of the at Bell Labs initiated a progressive miniaturization of electronic components that by the mid 1980s resulted in high density, which in turn led to tremendous advances in computer technology and computer based automated systems. 

What is Electronics

Electronics is the study of flow of electrons in various materials or space subjected to various conditions. In the past, electronics dealt with the study of Vacuum Tubes or Thermionic valves, today it mainly deals with flow of electrons in semiconductors. However, despite these technological differences, the main focus of electronics remains the controlled flow of electrons through a medium. By controlling the flow of electrons, we can make them perform special tasks, such as power an induction motor or heat a resistive coil.

Plumbing Analogy A simple way to understand electrical circuits is to think of them as pipes. Let's say you have a simple circuit with a voltage source and a resistor between the positive and negative terminals on the source. When the circuit is powered, electrons will move from the negative terminal, through the resistor, and into the positive terminal. The resistor is basically a path of conduction that resists the movement of electrons. This circuit could also be represented as a plumbing network. In the plumbing network, the resistor would be equivalent to a section of pipe, where the water is forced to move around several barriers to pass through, effectively slowing its flow. If the pipe is level, no water will flow in an organized fashion, since the pressure is equal throughout the pipe. However, if we tilt the pipe to a vertical position, a pressure difference is created and the water begins flowing through the pipe. This flow of water is similar to the flow of electrons in a circuit.

Device or technology associated with or employing low voltage current and solid state integrated circuits or components, usually for transmission and or processing of analog or digital data. 

The branch of physics and technology concerned with the design of circuits using transistors and microchips, and with the behavior and movement of electrons in a semiconductor, conductor, vacuum, or gas.

The electron is the negatively charged particle in an atom. It is also the smallest of the three subatomic particles. It stays outside of the nucleus in what are known as orbitals.

The concept electronics is used for electronic components, integrated circuits, and electrical systems. Main areas of usage are modern information technology and telecommunications, tools for recording and playing sound and picture, sensors and steering systems, instrumentation and measurement devices. Electronics, information technology and communication technology have undergone immense growth during the past 30 years. Our new technology based lives are run by the development of miniaturized electrical circuits and broadband phone and internet through optical fibers or across wireless channels.

Within transportation we have advanced electrical navigation systems, landing systems for planes, and anti-collision systems for ships and cars. Automatic toll stations across the biggest cities provide money for new roads and environmental friendly traffic. Modern cars are provided with constantly advancing electronics, such as airbag systems, ABS breaks, anti spin systems and theft alarms. 

Modern electronics has revolutionized medical diagnosis by introducing new techniques like CT computer tomography, MR, and ultrasound imaging devices. The industry applies electronics for controlling and supervising production processes and developing new technologies. 

Centrally in this picture we also have sensors that can feel sound, light, pressure, temperature acceleration, etc., and actuators that can perform specific operation such as turning on a switch or transmit sound signals. This advancement in technology and electronics will continue with increasing speed in times to come. 

Finally, computers have become common facilities in offices and at home. Through systematic miniaturization of electrical components and circuits, computers and other advanced electronics today are now available for ordinary users for moderate prices.

What is Electronics to Applications and Components

          Electronics means study of flow of electrons in electrical circuits. The word Electronics comes from electron mechanics which means learning the way how an electron behaves under different conditions of externally applied fields. IRE The Institution of Radio Engineers has given a definition of electronics as that field of science and engineering, which deals with electron devices and their utilization. Fundamentals of electronics are the core subject in all branches of engineering nowadays.

Application of Electronics

Electronics has made tremendous advancement during last few decades and our day to day life involves the use of electronic devices. Electronics has played a major role in every sphere of our life, this can be proved with the following application of electronics,

Entertainment and Communication
 

           Availability of economical and fast means of communication paves the way for progress of a country. Few decades ago, the main application of electronics was in the field of telephony and telegraphy. Now, with the aid of radio waves we can transmit any message from one place to another, without the use of wires. Radio and TV broadcasting offers a means of both entertainment as well as communication. Today, Electronics gadgets are widely used for entertainment.

Defence Applications

            Defence applications are completely controlled by electronic circuits. RADAR that is Radio Detection and Ranging is the most important development in electronics field. With the help of radar it is possible to detect and find the exact location of enemy aircraft. Radar and anti craft guns can be linked by an automatic control system to make a complete unit.

Industrial Application

Electronics circuits are widely being used in industrial applications such as control of thickness, quality, weight and moisture content of a material. Electronic amplifier circuits are used to amplify signals and thus control the operations of automatic door openers, power systems and safety devices. Electronically controlled systems are used for heating and welding in the industry. The most important industrial application is that the power stations which generate thousands of megawatts of electricity are controlled by 

Instrumentation  Application of Electronics

               Electronics instruments such as cathode ray oscilloscopes, frequency counters, signal generators, strain gauges are of great help in for precise measurement of various quantities. Without these electronic instruments no research laboratory is complete.

An Introduction to Electronic Components

               All electronic circuits contain few basic components. That are three passive components and two active components. An Integrated circuit may comprise of thousands of transistors, few capacitors on a small chip.

Types of Electronic Components

Passive Components

Resistors
Capacitors
 Inductors

Active Components

Tube devices
Semiconductor devices

What are Passive Components

        Resistors, capacitors and inductors are called as passive components. These electronics components are called passive because they by themselves are not capable of amplifying or processing an electrical circuit. However, passive components are as important as active components in any electronic circuit.

       Resistors: The component that opposes the flow of current is called a resistor. This opposing force is called the resistance of the material. It is measured in ohms.

Capacitors: Capacitor is a component that is used to store electrical energy and release them whenever desired. It is measured in farads. Capacitors like resistors can either be fixed or variable. Some common capacitors are mica, ceramic, paper and air gang capacitors.

Inductor: The electronic component which produces inductance is called an inductor. The inductance is measured in henrys. All inductors, like resistors and capacitors are listed as fixed and variable.

What are Active Components

          Active components are used in electronic circuits. They are classified in two categories, Tube devices and semiconductor devices. Due to many advantages of semiconductor devices, they are replacing tube devices in many electronic applications.

         Electronics components and electronic applications are penetrated everywhere in our day to day life. Electronics deals in the micro and milli range of voltage, current and power and also control kilo and mega volts, amperes and watts.

What Is the Difference between Electronic and Electrical Devices

                The first electric batteries were invented by a fellow named Alessandro Volta in 1800. Volta’s contribution is so important that the common volt is named for him. There is some archaeological evidence that the ancient Parthian Empire may have invented the electric battery in the second century BC, but if so we don’t know what they used their batteries for, and their invention was forgotten for 2,000 years.

                 The electric telegraph was invented in the 1830s and popularized in America by Samuel Morse, who invented the famous Morse code used to encode the alphabet and numerals into a series of short and long clicks that could be transmitted via telegraph. In 1866, a telegraph cable was laid across the Atlantic Ocean allowing instantaneous communication between the United States and Europe.

                    The answer lies in how devices manipulate electricity to do their work. Electrical devices take the energy of electric current and transform it in simple ways into some other form of energy  most likely light, heat, or motion. The heating elements in a toaster turn electrical energy into heat so you can burn your toast. And the motor in your vacuum cleaner turns electrical energy into motion that drives a pump that sucks the burnt toast crumbs out of your carpet.

                  In contrast, electronic devices do much more. Instead of just converting electrical energy into heat, light, or motion, electronic devices are designed to manipulate the electrical current itself to coax it into doing interesting and useful things.

                That very first electronic device invented in 1883 by Thomas Edison manipulated the electric current passing through a light bulb in a way that let Edison create a device that could monitor the voltage being provided to an electrical circuit and automatically increase or decrease the voltage if it became too low or too high.

               One of the most common things that electronic devices do is manipulate electric current in a way that adds meaningful information to the current. For example, audio electronic devices add sound information to an electric current so that you can listen to music or talk on a cell phone. And video devices add images to an electric current so you can watch great movies until you know every line by heart.

              Keep in mind that the distinction between electric and electronic devices is a bit blurry. What used to be simple electrical devices now often include some electronic components in them. For example, your toaster may contain an electronic thermostat that attempts to keep the heat at just the right temperature to make perfect toast.

             And even the most complicated electronic devices have simple electrical components in them. For example, although your TV set remote control is a pretty complicated little electronic device, it contains batteries, which are simple electrical devices.

Electricity and Matter

All matter interacts with Electricity, and are divided into three categories Conductors, Semi Conductors, and Non Conductors.

Matter that conducts Electricity easily. Metals like Zinc and Copper conduct electricity very easily. Therefore, they are used to make Conductors.

Matter that does not conduct Electricity at all. Non Metals like Wood and Rubber do not conduct electricity so easily. Therefore, they are used to make Non Conductors.

Matter that conducts electricity in a manner between that of Conductors and Non Conductors. For example, Silicon and Germanium conduct electricity better than non conductors but worse than conductors. Therefore, they are used to make Semi Conductors.

Electricity and Conductors

Normally, all conductors have a zero net charge. If there is an electric force that exerts a pressure on the charges in the conductor to force charges to move in a straight line result in a stream of electric charge moving in a straight line.

Electronic component

An electronic component is any basic discrete device or physical entity in an electronic system used to affect or their associated fields. Electronic components are mostly industrial products, available in a singular form and are not to be confused with, which conceptual abstractions are representing idealized electronic components.

Electronic components have two or more electrical aside from which may only have one terminal. These leads connect, usually to a printed circuit board, to create with a particular function. Basic electronic components may be packaged discretely, as arrays or networks of like components, or integrated inside of packages such as, semiconductor integrated circuits, hybrid integrated circuits, or thick film devices. The following list of electronic components focuses on the discrete version of these components, treating such packages as components in their own right.

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Classification

A component may be classified as, or electro mechanic. The strict physics definition treats passive components as ones that cannot supply energy themselves, whereas a would be seen as an active component since it truly acts as a source of energy.

However, who perform use a more restrictive definition of passivity. When only concerned with the energy of, it is convenient to ignore the so called circuit and pretend that the power supplying components such as or is absent, though it may in reality be supplied by the DC circuit. Then, the analysis only concerns the AC circuit, an abstraction that ignores DC voltages and currents present in the real life circuit. This fiction, for instance, lets us view an oscillator as producing energy even though in reality the oscillator consumes even more energy from a DC power supply, which we have chosen to ignore. Under that restriction, we define the terms as used in as,

Active components: rely on a source of energy and usually can inject power into a circuit, though this is not part of the definition. Active components include amplifying components such as, triode, and tunnel diodes.

Passive components: can't introduce net energy into the circuit. They also can't rely on a source of power, except for what is available from the circuit they are connected to. As a consequence they can't amplify, although they may increase a voltage or current. Passive components include two terminal components such as resistors, capacitors, inductors, and transformers.

 

Electromechanical components: can carry out electrical operations by using moving parts or by using electrical connections. Most passive components with more than two terminals can be described in terms of that satisfy the principle of though there are rare exceptions. In contrast, active components generally lack that property.

Definition of Electronics

Electronics is the branch of science that deals with the study of flow and control of electrons and the study of their behavior and effects in vacuums, gases, and semiconductors, and with devices using such electrons. This control of electrons is accomplished by devices that resist, carry, select, steer, switch, store, manipulate, and exploit the electron.

         Some of the basic electrical units and definitions are mentioned below,

            Passive: Capable of operating without an external power source. Typical passive components are resistors, capacitors, inductors and diodes.

Active: Requiring a source of power to operate.    Includes transistors, integrated circuits,TRIACs, SCRs, LEDs, etc.

DC: Direct Current. The electrons flow in one direction only.  Current flow is from negative to positive, although it is often more convenient to think of it as from positive to negative.  This is sometimes referred to as conventional current as opposed to electron flow.

AC: Alternating Current. The electrons flow in both directions in a cyclic manner  first one way, then the other.  The rate of change of direction determines the frequency, measured in Hertz.

Frequency: Unit is Hertz, Symbol is Hz, old symbol was cps. A complete cycle is completed when the AC signal has gone from zero volts to one extreme, back through zero volts to the opposite extreme, and returned to zero.  The accepted audio range is from 20Hz to 20,000Hz.  The number of times the signal completes a complete cycle in one second is the frequency.

Voltage: Unit is Volts, Symbol is V or U, old symbol was E . Voltage is the pressure of electricity, or electromotive force.  A 9V battery has a voltage of 9V DC, and may be positive or negative depending on the terminal that is used as the reference.  The mains has a voltage of 220, 240 or 110V depending where you live this is AC, and alternates between positive and negative values.  Voltage is also commonly measured in millivolts, and 1,000 mV is 1V.  Microvolts and nanovolts are also used.

Current: Unit is Amperes, Symbol is I. Current is the flow of electricity. No current flows between the terminals of a battery or other voltage supply unless a load is connected.  The magnitude of the current is determined by the available voltage, and the resistance of the load and the power source.  Current can be AC or DC, positive or negative, depending upon the reference.  For electronics, current may also be measured in mA 1,000 mA is 1A.  Nanoamps are also used in some cases.

Resistance: Unit is Ohms, Symbol is R or Resistance is a measure of how easily electrons will flow through the device.  Copper wire has a very low resistance, so a small voltage will allow a large current to flow.  Likewise, the plastic insulation has a very high resistance, and prevents current from flowing from one wire to those adjacent.  Resistors have a defined resistance, so the current can be calculated for any voltage.  Resistance in passive devices is always positive.