LEARNINGOBJECTIVESUpon completion and review of this chapter, youshould be able to:

• Define electricity, atomic structure, and elec-tron movement and explain atomic theory inrelation to battery operation, using like andunlike charges.

• Explain the different sources of electricity.• Describe the scientists who were instrumen-

tal in the development of the different tenetsof electrical theory.

KEY TERMSAmberAtomBatteryCurrentElectricityElectrolyteElectronElectrostatic Discharge (ESD)HorsepowerIonMatterNeutronNucleusPhotoelectricityPiezoelectricityProtonStatic ElectricityThermocoupleThermoelectricityValenceVoltage

INTRODUCTIONThis chapter reviews what electricity is in its basicform. We will look at natural forms of electricalenergy, and the people who have historically playeda part in developing the theories that explain elec-tricity. It is extremely important for automotivetechnicians to learn all that they can about basicelectricity and electronics, because in today’s mod-ern automobile, there is a wire or computer con-nected to just about everything.

21

2Introduction toElectricity

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22 Chapter Two

Many of us take for granted the sources of elec-tricity. Electricity is a natural form of energy thatcomes from many sources. For example, electric-ity is in the atmosphere all around us; a generatorjust puts it in motion. We cannot create or destroyenergy, only change it, yet we can successfullyproduce electricity and harness it by changingvarious other forms of natural energy.

WHAT ISELECTRICITY?Was electricity invented or discovered? The answeris that electricity was discovered. So who discoveredelectricity? Ben Franklin? Thomas Edison figuredout how to use electricity to make light bulbs, recordplayers, and movies. But neither of these scientist/inventors had anything to do with the discovery ofelectricity.

Actually, the Greeks discovered electricity.They found that if they took amber (a translu-cent, yellowish resin, derived from fossilizedtrees) and rubbed it against other materials, itbecame charged with an unseen force that had theability to attract other lightweight objects such asfeathers, somewhat like a magnet picks up metalobjects. In 1600, William Gilbert published abook describing these phenomena. He also dis-covered that other materials shared the ability toattract, such as sulfur and glass. He used the Latinword “elektron” to describe amber and the word“electrica” for similar substances. Sir ThomasBrowne first used the word electricity during the1600s. Two thousand years after ancient Greece,electricity is all around us. We use it every day.But what exactly is electricity? You can’t see it.You can’t smell it. You can’t touch it; well, youcould touch it, but it would probably be ashocking experience and could cause seriousinjury. Next, we will discuss atomic structure tofind a more exact definition of electricity.

ATOMIC STRUCTUREWe define matter as anything that takes upspace and, when subjected to gravity, has weight.There are many different kinds of matter. OnEarth, we have classified over a hundred ele-ments. Each element is a type of matter that hascertain individual characteristics. Most havebeen found in nature. Examples of natural ele-

ments are copper, iron, gold, and silver. Otherelements have been produced only in the labora-tory. Every material we know is made up of oneor more elements.

Let’s say we take a chunk of material—a rockwe found in the desert, for example—and beginto divide it into smaller parts. First we divide itin half. Then we test both halves to see if it stillhas the same characteristics. Next we take one ofthe halves and divide it into two parts. We testthose two parts. By this process, we might dis-cover that the rock contains three different ele-ments. Some of our pieces would have the char-acteristics of copper, for example. Others wouldshow themselves to be carbon, yet others wouldbe iron.

AtomsIf you could keep dividing the material indefi-nitely, you would eventually get a piece that onlyhad the characteristics of a single element. At thatpoint, you would have an atom, which is the small-est particle into which an element can be dividedand still have all the characteristics of that element.An atom is the smallest particle that has the char-acteristic of the element. An atom is so small that itcannot be seen with a conventional microscope,even a very powerful one. An atom is itself madeup of smaller particles. You can think of these asuniversal building blocks. Scientists have discov-ered many particles in the atom, but for the purposeof explaining electricity, we need to talk about justthree: electrons, protons, and neutrons.

All the atoms of any particular element lookessentially the same, but the atoms of each ele-ment are different from those of another element.All atoms share the same basic structure. At thecenter of the atom is the nucleus, containingprotons and neutrons, as shown in Figure 2-1.Orbiting around the nucleus, in constant motion,are the electrons. The structure of the atom resem-bles planets in orbit around a sun.

The exact number of each of an atom’sparticles—protons, neutrons, and electrons—depends on which element the atom is from. Thesimplest atom is that of the element hydrogen. Ahydrogen atom (Figure 2-1) contains one proton,one neutron, and one electron. Aluminum, bycomparison, has 13 protons, 14 neutrons, and13 electrons. These particles—protons, neu-trons, and electrons—are important to usbecause they are used to explain electrical

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Introduction to Electricity 23

Figure 2-1. In an atom (left), electrons orbit protons inthe nucleus in the same way the planets orbit the Sun.

charges, voltage, and current. Electrons orbit thenucleus of an atom in a concentric ring known asa shell. The nucleus contains the proton and theneutron, which contains almost all of the massof the entire atom.

There are two types of force at work in everyatom. Normally, these two forces are in balance.One force comes from electrical charges and theother force, centrifugal force, is generated whenan object moves in a circular path.

Electrical ChargesNeutrons have no charge, but electrons have anegative electrical charge. Protons carry a posi-tive electrical charge (Figure 2-2). Opposite elec-trical charges always attract one another; so parti-cles or objects with opposite charges tend to movetoward each other unless something opposes the

attraction. Like electrical charges always repel;particles and objects with like charges tend tomove away from each other unless the repellingforce is opposed.

In its normal state, an atom has the same num-ber of electrons as it does protons. This means theatom is electrically neutral or balanced becausethere are exactly as many negative charges asthere are positive charges. Inside each atom, neg-atively charged electrons are attracted to posi-tively charged protons, just like the north andsouth poles of a magnet, as shown in Figure 2-3.Ordinarily, electrons remain in orbit because thecentrifugal force exactly opposes the electricalcharge attraction. It is possible for an atom to loseor gain electrons. If an atom loses one electron,the total number of protons would be one greaterthan the total number of electrons. As a result, theatom would have more positive than negativecharges. Instead of being electrically neutral, theatom itself would become positively charged.

All electrons and protons are alike. The num-ber of protons associated with the nucleus of anatom identifies it as a specific element. Electronshave 0.0005 of the mass of a proton. Under nor-mal conditions, electrons are bound to the posi-tively charged nuclei of atoms by the attractionbetween opposite electrical charges.

The electrons are in different shells or dis-tances from the nucleus. The greater the speed,the higher the energy of the electrons, the furtheraway from the nucleus the electron orbit. All ele-ments are composed of atoms and each elementhas its own characteristic number of protonswith a corresponding equal number of electrons.The term electricity is used to describe thebehavior of these electrons in the outer orbits ofthe atoms.

Electric Potential—VoltageWe noted that a balance (Figure 2-4) betweencentrifugal force and the attraction of opposingcharges keeps electrons in their orbits. If any-thing upsets that balance, one or more electronsmay leave orbit to become free electrons. When

Figure 2-2. The charges within an atom.

Figure 2-3. Unlike and like charges of a magnet.

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a number of free electrons gather in one location,a charge of electricity builds up. This chargemay also be called a difference in electric“potential”. This difference in electric potentialis more commonly known as voltage and can becompared to a difference in pressure that makeswater flow. When this potential or pressurecauses a number of electrons to move in a singledirection, the effect is current flow. So the defi-nition of current is the flow of electrons. Anyatom may possess more or fewer electrons thanprotons. Such an unbalanced atom would bedescribed as negatively (an excess of electrons)or positively (a net deficit of electrons) chargedand known as an ion (Figure 2-5). An ion is anatom that has gained or lost an electron. Ions tryto regain their balance of equal protons and elec-trons by exchanging electrons with nearbyatoms. This is known as the flow of electriccurrent or electricity. For more informationabout voltage and current, see the section on“Electrical Units of Measurement” in Chapter 3of the Shop Manual.

24 Chapter Two

Figure 2-5. An unbalanced atom.

ValenceThe concentric orbital paths, or shells, of an atomproceed outward from the nucleus. The electronsin the shells closest to the nucleus of the atom areheld most tightly while those in the outermostshell are held more loosely. The simplest element,hydrogen, has a single shell containing one elec-tron. The most complex atoms may have sevenshells. The maximum number of electrons thatcan occupy shells one through seven are, insequence: 2, 8, 18, 32, 50, 72, 98. The heaviestelements in their normal states have only the firstfour shells fully occupied with electrons; theouter three shells are only partially occupied. Theoutermost shell in any atom is known as itsvalence ring. The number of electrons in thevalence ring will dictate some basic characteris-tics of an element.

The chemical properties of atoms are definedby how the shells are occupied with electrons. Anatom of the element helium whose atomic numberis 2 has a full inner shell. An atom of the elementneon with an atomic number of 10 has both a fullfirst and second shell (2 and 8): its second shell isits valence ring (Figure 2-6). Other more complexatoms that have eight electrons in their outermostshell, even though this shell might not be full, willresemble neon in terms of their chemical inert-ness. Valence represents the ability to combine.

Remember that an ion is any atom with either asurplus or deficit of electrons. Free electrons canrest on a surface or travel through matter (or a vac-uum) at close to the speed of light. Electrons restingon a surface will cause it to be negatively charged.

Figure 2-4. A balanced atom.

Copper AtomSingle

ValenceElectron

Figure 2-6. Valence ring.

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Introduction to Electricity 25

Because the electrons are not moving, that surfaceis described as having a negative static electricalcharge. The extent of the charge is measured involtage or charge differential. A stream of movingelectrons is known as an electrical current. Forinstance, if a group of positive ions passes in closeproximity to electrons resting on a surface, they willattract the electrons by causing them to fill the“holes” left by the missing electrons in the positiveions. Current flow is measured in amperes: oneampere equals 6.28 × 1018 electrons (1 coulomb)passing a given point per second.

SOURCES OFELECTRICITYLightningBenjamin Franklin (1706–1790) proved the electri-cal nature of thunderstorms in his famous kiteexperiment, established the terms positive andnegative, and formulated the conventional theory of

current flow in a circuit. Franklin was trying toprove that the positive and negative electron distri-bution in the clouds produced the static electricitythat causes lightning, as shown in Figure 2-7.Natural negatively charged particles will producelightning when they find a path negative to positive.

Benjamin Franklin’s Theory:

When the science of electricity was still young,the men who studied it were able to use electric-ity without really understanding why and how itworked. In the early 1700s, Benjamin Franklin, theAmerican printer, inventor, writer, and politician,brought his famed common sense to the problem.Although he was not the first to think that electric-ity and lightning were the same, he was the first toprove it. He also thought that electricity was like afluid in a pipe that flowed from one terminal to theother. He named the electrical terminals positiveand negative and suggested that current movedfrom the positive terminal to the negative terminal.Benjamin Franklin created what we now call theConventional Theory of Current Flow.

Lightning Can Travelfrom Cloud to Cloud

Lightning Can Travelfrom GROUND to Cloud

Lightning Can Travelfrom Cloud to GROUND

Positively ChargedCloud Negatively

ChargedCloud

Figure 2-7. Electron charges in the earth’s atmosphere.

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26 Chapter Two

Figure 2-8. Static electricity discharge to metal object.

Plastic Comb withA Negative ChargeAfter Combing Hair

Small Pieces of Paper

Figure 2-9. Static electricity discharge attraction.

Static ElectricityStatic electricity is the term used to describe anelectrical charge that can build up in insulation byfriction or movement. It is referred to as staticelectricity because, until the electrical charge isdissipated, the electrons are not moving. SeeFigure 2-8. Static can be created by any one of thefollowing examples:

• Walking on carpet or vinyl floors• Movement between clothing and the body

causes friction• Combing hair with a plastic comb

These actions cause the electrons to be pulledfrom an object, thereby creating a negative chargeon one, such as the comb, and a positive charge tothe other, such as the hair. The charges created canbe shown as in Figure 2-9, which illustrates thatlike charges repel each other, whereas unlikecharges are attracted toward each other.

The static charges that build up are not dis-charged until a conductor, such as a metal object,is touched.

Static electricity can also be referred to asfrictional electricity because it results from thecontact of two surfaces. Chemical bonds areformed when any surfaces contact and if theatoms on one surface tend to hold electrons

more tightly, the result is the theft of electrons.Such contact produces a charge imbalance bypulling electrons of one surface from that of theother; as electrons are pulled away from a sur-face, the result is an excess of electrons (nega-tive charge) and a deficit in the other (positivecharge). The extent of the charge differential is,of course, measured in voltage. While the sur-faces with opposite charges remain separate, thecharge differential will exist. When the twopolarities of charge are united, the chargeimbalance will be canceled. Static electricity isan everyday phenomenon, as described in theexamples in the opening to this chapter, and itinvolves voltages of 1,000 volts to 50,000 volts.An automotive technician should always use astatic grounding strap when working with sta-tic-sensitive electronic devices such as PCMsand ECMs.

Electrostatic FieldThe attraction between opposing electricalcharges does not require contact between theobjects involved, as shown in Figure 2-10. Thisis so because invisible lines of force exist arounda charged object. Taken all together, these linesof force make up an electrostatic field. Suchfields are strongest very close to the chargedobject and get weaker as they extend away fromthe object.

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Introduction to Electricity 27

Figure 2-10. Electrostatic field.

Figure 2-11. ESD symbol.

Electrostatic Discharge (ESD)An electrostatic charge can build up on the sur-face of your body. If you touch something, yourcharge can be discharged to the other surface.This is called electrostatic discharge (ESD).Figure 2-11 shows what the ESD symbol lookslike. The symbol tells you that the component is asolid-state component. Some service manualsuse the words “solid-state” instead of the ESDsymbol. Look for these indicators and takethe suggested ESD precautions when you workon sensitive components. We will cover this sub-ject in detail in Chapter 10 of this manual.

Chemical SourceA battery creates electricity by chemical reactionby the lead dioxide and lead plates submerged ina sulfuric acid electrolyte. In any battery, the

chemical reaction that occurs releases electronsand generates direct current (DC) electricity. See Figure 2-12. An electrolyte is a chemical solu-tion that usually includes water and other com-pounds that conduct electricity. In the case ofautomotive battery, the solution is water and sul-furic acid.

When the battery is connected into a completedelectrical circuit, current begins to flow from thebattery. This current is produced by chemical reac-tions between the active materials in the two kindsof plates and the sulfuric acid in the electrolyte(Figure 2-12). The lead dioxide in the positiveplate is a compound of lead and oxygen. Sulfuricacid is a compound of hydrogen and the sulfateradical. During discharge, oxygen in the positiveactive material combines with hydrogen in theelectrolyte to form water. At the same time, lead inthe positive active material combines with the sul-fate radical, forming lead sulfate. Figure 2-13

Negative PlateLead

Positive PlateLead Dioxide

ElectrolyteSulfuricAcid

Figure 2-12. Automotive battery operation.

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28 Chapter Two

Voltmeter

Lemon Battery

Figure 2-13. Lemon powered battery.

Pyrometer

200 300 400 500 600

Voltmeter

Thermocouple

Exhaust Temp. ºF

Figure 2-14. Pyrometer thermocouple.

shows a very simplified version of a battery pow-ered by a lemon. The availability and amount ofelectrical energy that can be produced in this man-ner is limited by the active area and weight of thematerials in the plates and by the quantity of sul-furic acid in the electrolyte. After most of theavailable active materials have reacted, the batterycan produce little or no additional energy, and thebattery is then discharged.

ThermoelectricityApplying heat to the connection point of two dis-similar metals can create electron flow (electricity),which is known as thermoelectricity (Figure 2-14). This affect was discovered by a German scien-tist named Seebeck and is known as the SeebeckEffect. Seebeck called this device a thermocouple,which is a small device that gives off a low voltagewhen two dissimilar metals are heated. An exampleof a thermocouple is a temperature measuringdevice called a pyrometer. A pyrometer is com-monly used to measure exhaust gas temperatureson diesel engines and other temperature measur-ing applications. A pyrometer is constructed oftwo dissimilar metals, such as steel and a copper

alloy, which is then connected to a voltmeter. Asthe temperature at the connections of the twometals increases, the reading on the voltmeterincreases. The voltmeter can then be calibrated indegrees.

PhotoelectricityLight is composed of particles called photons thatare pure energy and contain no mass. However,when sunlight contacts certain materials, such asselenium and cesium, electron flow is stimulatedand is called photoelectricity (Figure 2-15).Photoelectricity is used in photoelectric cells,which are used in ambient light sensors. Solarenergy is light energy from the sun that is gath-ered in a photovoltaic solar cell.

PiezoelectricitySome crystals, such as quartz or barium titanate,create a voltage if pressure is applied. A change inthe potential of electrons between the positive andnegative terminal creates electricity know aspiezoelectricity. The term comes from the Greekword “piezo,” which means pressure. Figure 2-16shows that when these materials, quartz or bariumtitanate, undergo physical stress or vibration, asmall oscillating voltage is produced.

Piezoelectricity is the principle used in knocksensors (KS), also called detonation sensors. Thetypical knock sensor (Figure 2-17) producesabout 300 millivolts of electricity and vibrates ata 6,000-hertz (cycles per second) frequency,which is the frequency that the cylinder wallsvibrate at during detonation.

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Introduction to Electricity 29

Neon Lamp

Hard Rubber Cushion

Barium Titanate

Hard Rubber Cushion

Figure 2-16. Piezoelectric effect.

Figure 2-15. Photoelectric cell sensor.

Figure 2-17. Piezoelectric knock sensor. (GM Serviceand Parts Operations)

voltage is generated between the faces of thecrystal. Although the effect is only temporary,while the pressure lasts, it can be maintained byalternating between compression and tension.Piezoelectricity is put to practical use in phono-graph pickups and crystal microphones, wheremechanical vibrations (sound waves) are con-verted into varying voltage signals. Similar appli-cations are used in underwater hydrophones andpiezoelectric stethoscopes.

Applying a high-frequency alternating voltageto a crystal can create a reverse piezoelectriceffect. The crystal then produces mechanicalvibrations at the same frequency, which are calledultrasonic sound waves because they are beyond

Squeeze a Rock Get a Volt

In 1880, the French chemists Pierre and MarieCurie discovered the phenomenon of piezoelec-tricity, which means, “electricity through pres-sure.” They found that when pressure is applied toa crystal of quartz, tourmaline, or Rochelle salt, a

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30 Chapter Two

1 Horsepower = a Horsepulling a 200 lb weight 165

feet in 1 minute

165 feet

Time1 Minute

200Pounds

200 time 165 = 33,000 lb/ft of work1 horse can do 33,000 lb/ft of

work in 1 minute

Figure 2-18. Horsepower.

our range of hearing. These ultrasonic vibrationsare used, among other things, to detect sonarreflections from submarines and to drill holes indiseased teeth.

HISTORICALFIGURES INELECTRICITYIn 1767, Joseph Priestly established that electri-cal charges attract with a force inversely propor-tional to distance. In 1800, Alessandro Voltainvented the first battery. Michael Faraday(1791–1867) opened the doors of the science wenow know as electromagnetism when he pub-lished his law of induction, which simply statesthat a magnetic field induces an electromotiveforce in a moving conductor. Thomas Edison(1847–1931) invented the incandescent lamp in1879, but perhaps even more importantly, builtthe first central power station and electrical distri-bution system in New York City in 1881. Thisprovided a means of introducing electrical powerinto industry and the home.

The discovery of the electron by J.J. Thomson(1856–1940) in 1897 introduced the science ofelectronics and quickly resulted in the inven-tion of the diode (1904), the triode (1907), andthe transistor (1946). Andre Marie Ampereestablished the importance of the relationshipbetween electricity and magnetism. In 1800,Alessandro Volta discovered that if two dissim-ilar metals were brought in contact with asalt solution, a current would be produced,this invention is now known as the battery.The German physicist George Simon Ohm(1787–1854) proved the mathematical relation-ship between electrical potential (voltage),electrical current flow (measured in amperes)and the resistance to the current flow (mea-sured in ohms: symbol Ω).

Another person who influenced electricaltechnology was a Scottish inventor namedJames Watt (1736–1819). James Watt workedin coal mines and saw the power of a horse as it

was used to lift coal from deep in the earth. Hedeveloped the steam engine to take over the taskof lifting heavy loads instead of using the powerof a horse. At the same time, he calculated thework that a horse could do and determined that ahorse could walk 165 feet in one minute pullinga 200-pound weight (165 ft. 200 lb. 33,000ft.-lb. per minute, or 550 foot-pounds of workper second) and called this amount of work onehorsepower. One horsepower is needed to lift550 pounds 1 foot off the ground in 1 second,one horsepower equals 33,000 foot-pounds ofwork per minute. The term brake horsepowercomes from the method of testing the earlyengines.

In the metric system, the power of engines ismeasured in watts or kilowatts after James Watt.Watt’s Law states that a watt is the power done bymoving one ampere through a resistance of oneohm using one volt in one second. Horsepowercan also be expressed in units of electrical poweror watts; the simple conversion is 1 horsepower= 746 watts.

The term watt is most commonly used toexpress electrical power, such as the wattage oflight bulbs. A light bulb is an example of wherewatts are commonly used. A 100-watt light bulbrequires more electrical power to light than a 60-watt bulb. Electricity is sold in kilowatt hours. Akilowatt is 1000 watts and a kilowatt hour is onekilowatt of power being used for one hour.

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Introduction to Electricity 31

SUMMARYThe Greeks discovered the first type of electricityin the form of static electricity when they observedthat amber rubbed with fur would attract light-weight objects such as feathers. Static electricity iselectricity at rest or without any motion. All matteris composed of atoms and electrical charge is acomponent of all atoms, so all matter is electricalin essence. An atom is the smallest part of an ele-ment that retains all of the properties of that ele-ment. All atoms share the same basic structure. Atthe center of the atom is the nucleus, containingprotons, neutrons, and electrons. When an atom isbalanced, the number of protons will match thenumber of electrons and the atom can be describedas being in an electrically neutral state. The phe-nomenon we describe as electricity concerns thebehavior of atoms that have become, for whateverreason, unbalanced or ionized. Electricity may bedefined as the movement of free electrons from oneatom to another.

An electrostatic charge can build up on the sur-face of your body. If you touch something, yourcharge can be discharged to the other surface,which is called electrostatic discharge (ESD). Anautomotive technician should always use a sta-tic grounding strap when working with static-sensitive electronic devices.

When light contacts certain materials, such asselenium and cesium, electron flow is stimulatedand is called photoelectricity. Solar energy is lightenergy (photons) from the sun that is gathered in aphotovoltaic solar cell. A photon is pure energythat contains no mass. Thermoelectricity is elec-tricity produced when two dissimilar metals areheated to generate an electrical voltage. A thermo-couple is a small device made of two dissimilarmetals that gives off a low voltage when heated.Piezoelectricity is electricity produced when mate-rials such as quartz or barium titanate are placedunder pressure. The production of electricity fromchemical energy is demonstrated in the lead-acidbattery. Electromagnetic induction is the produc-tion of electricity when a current is carried througha conductor and a magnetic field is produced.

Andre Marie Ampere established the impor-tance of the relationship between electricity andmagnetism. Alessandro Volta discovered that iftwo dissimilar metals were brought in contactwith a salt solution, a current would be pro-duced; this invention is now known as the bat-tery. George Simon Ohm showed a relationshipbetween resistance, current, and voltage in anelectrical circuit; he developed what is known asOhm’s Law. James Watt developed a methodused to express a unit of electrical power knownas Watt’s Law.

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32 Chapter Two

Review Questions1. The general name given every substance in

the physical universe is which of thefollowing:a. Massb. Matterc. Compoundd. Nucleus

2. The smallest part of an element that retainsall of its characteristics is which of thefollowing:a. Atomb. Protonc. Compoundd. Neutron

3. The particles that orbit around the center ofan atom are called which of the following:a. Electronsb. Moleculesc. Nucleusd. Protons

4. An atom that loses or gains one electron iscalled which of the following:a. Balancedb. An elementc. A moleculed. An ion

5. Technician A says the battery provideselectricity by releasing free electrons.Technician B says the battery stores energyin a chemical form. Who is right?a. A onlyb. B onlyc. Both A and Bd. Neither A nor B

6. Static electricity is being discussed.Technician A says that static electricity iselectricity in motion. Technician B says anelectrostatic charge can build up on thesurface of your body. Who is right?a. A onlyb. B onlyc. Both A and Bd. Neither A nor B

7. What people discovered electricity?a. The Italiansb. The Germansc. The Greeksd. The Irish

8. Technician A says batteries produce directcurrent from a chemical reaction.Technician B says that an electrolyte is achemical solution of water andhydrochloric acid that will conductelectricity. Who is right?a. A onlyb. B onlyc. Both A and Bd. Neither A nor B

9. Two technicians are discussingthermoelectricity. Technician A saysapplying heat to the connection point of twodissimilar metals can create electron flow(electricity). Technician B says athermocouple is a small device made of twodissimilar metals that gives off a low voltagewhen heated. Who is right?a. A onlyb. B onlyc. Both A and Bd. Neither A nor B

10. Technician A says when sunlight contactscertain materials, electron flow is stimulated.Technician B says solar energy is lightenergy from the moon that is gathered in aphotovoltaic solar cell. Who is right?a. A onlyb. B onlyc. Both A and Bd. Neither A nor B

11. Two technicians are discussing howpiezoelectricity works. Technician A says itis electricity produced when barium titanateis placed under pressure. Technician Bsays when no change in the potential ofelectrons between positive and negativeterminal occurs, the barium titanate createselectricity. Who is right?a. A onlyb. B onlyc. Both A and Bd. Neither A nor B

12. James Watt’s term horsepower is beingdiscussed. Technician A says onehorsepower equals 33,000 foot-pounds ofwork per hour. Technician B says onehorsepower would be produced when ahorse walked 165 feet in one minute pulling

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Introduction to Electricity 33

a 500-pound weight or 165 ft. × 500 lb. =33,000 ft-lb. Who is right?a. A onlyb. B onlyc. Both A and Bd. Neither A nor B

13. Technician A says Andre Marie Ampereestablished the importance of therelationship between electricity and

magnetism. Technician B says AlessandroVolta discovered that if two dissimilar metalswere brought in contact with a watersolution, a current would be produced. Whois right?a. A onlyb. B onlyc. Both A and Bd. Neither A nor B

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