Basic Electricity 1

8/8/2019 Basic Electricity 1

1/20

STUDY COURSEfor Home Appliances

UNDERSTANDING:

ELECTRICAL WIRING

ALTERNATING CURRENT

DIRECT CURRENT

Module 1LIT 787739 Rev. B

BASIC ELECTRICITY

WALLRECEPTACLE

APPLIANCECORD


2/20

All right s reser ved. No port ion of th is book may be repr oduced in any form with out

written permission from WHIRLPOOL CORPORATION.

1989, 1993, 2000 WHIRLPOOL CORPORATION

WHIRLPOOL CORPORATION does not assu me an y responsibilityor a ny liability in conn ection with t he u se of th is ma nu al.

The tra demarks WHIRLPOOL , , , andFSP ar e registered

trademarks of Whirlpool Corporation.


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INTRODUCTION

The material presented in this module is intended to provide you with an understanding of the

fun dam enta ls of electricity as a pplied t o major appliances.

Major appliances ha ve become more sophisticat ed, tak ing th em out of th e screwdriver a nd pliers category.

Their electrical circuits include several different types of automatic controls, switches, heaters, valves, etc..

Semiconductors, solid-state controls, and other components usually associated with radio and television

electr onic circuits, are being engineered int o automa tic washers, dryers, dishwa shers, a nd r efrigerators.

The appliance technician is emerging into a professiona l stat us of his own. He must prepar e himself now

to be able to perform his du ties today as well as t o retain h is professiona lism in th e futur e.

No longer is on-the-job training sufficient to prepare technicians for the complicated procedures required

for todays sophisticated appliances. This tra ining can best be obtained thr ough organized classroom st udy

and application. However, much of the knowledge necessary to service todays appliances can be obtained

thr ough stu dy cour ses. Completion of this a nd other courses will provide you with su fficient u nderst an ding of

appliances and their operation to enable you to do minor service. It will also serve as a valuable stepping

stone to m ore advan ced st udy a nd on-th e-job tr aining t o improve your ser vicing skills.

Informa tion conta ined in t his module is used on WHIRLPOOL applian ces.

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TABLE of CONTEN TS

PAGE

CHAP TER 1 ..............................................................................................3Electical Wiring

CHAP TER 2 ..............................................................................................8Alternating Current

CHAP TER 3 ..............................................................................................9Direct Current

*TEST ............................................................See Test Book LIT787743

*NOTE: We recomm end ta k ing the TEST for MODULE 1, r igh t

a fter s tud ying i t .

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CHAPTER 1

ELECTRICAL WIRIN G

Before we get sta rt ed in t his ba sic electricity course, lets simplify how electricity

flows from your citys power source t o inside your home.

Look at a road map and pick out a major highway from one location to another.

This would be the same as electricity flowing from a power source to a step-up

(increases voltage) transformer. Transformers are used to hold AC voltage over long

distances.

Do you see sma ll roads you can tu rn onto, off the m ajor h ighway? This is like th e

power lines going to differen t h omes.

At the intersection of the small road and major highway, there is a step-down

(decreases voltage) transformer. This transformer reduces the AC voltage to your

home.

Now pictu re yourself going down t he sm all road an d into th e city with a ll the city

street s. These streets a re like wiring inside your home.

All the st reets, roads, an d th e major highway ar e connected t ogether . This is like

having electricity flowing from the power source to all the outlets in your home.

But wha t if someth ing doesnt work? It could be a brea k in th e road (power line). In

oth er words, say t here is a d rawbr idge (like a switch) over wat er. As you drive down

the road (like electricity flows), a small sail boat decides to go under the drawbridge

(switch). The dra wbridge (switch) opens, st opping th e flow of tra ffic (electr icity). In

order for t he tr affic (electricity) to sta rt flowing aga in, th e dra wbridge (switch) ha s to

be lowered.

3


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WHAT IS A CIRCU IT?

A circuit is a complete path for electricity to flow

through.

This is a n exa mple of a complete circuit. It is called a

complet e or closed circuit, becaus e th e electr icity can

flow all the way from point A to point B without

interruption.

This is not a complete circuit. There is a brea k in t he

pat h where th e electricity (cur rent ) can flow.

Sometimes a br eak in th e circuit is caused by design.

For example, when we turn a switch to its OFF

position, we cause a break in th e circuit.

4

Sometimes a break is caused by accident, and then

YOU ha ve to find out wh ere it is.

When there is a break in t he circuit , we say that the

circuit is OPEN. An OPE N circuit is one tha t cann ot

operate because th ere is a break in th e path thr ough

which t he curr ent m ight flow.

A CLOSED circuit is one in wh ich t her e is a complet e

pat h for th e electricity to follow.

CIRCUIT COMPONENTS

Circuits could have up to four kinds of components.

There m ust be a power source and a condu ctor for a ny

type of circuit.

1. A Power Source might be a ba tter y, or it could be

the electricity coming from the wall outlet.

2. Condu ctors will usua lly be a wire, and even

sometimes the metal chassis (frame) on which the

component s are mount ed.

3. Loads are th e components t hat do all the work.

For example, motors turn the agitator in washing

machines, move the hands on clocks, and turn fanblades. Other examples of loads would be resistors,

solenoids, and light bulbs. A load is anything that

uses up some of th e electr icity flowing thr ough the

circuit.

4. Contr ols ar e devices th at control the flow of

electr icity to th e load s. A contr ol is usu ally some sort

of switch th at is operat ed by the us er of th e appliance,

or operat ed by th e applian ce itself.

A B

LIGHT BULB

BREAK

A B

A B

SWITCH

A B

OPEN CIRCUIT

A B

CLOSED CIRCUIT


7/205

We will now cover t hr ee kind s of circuits .

1. Ser ies ci rcui ts

2. Paral lel ci rcui ts

3. Series-par allel circuits (which are combinat ions of

the first t wo kinds).

SERIES CIRCUITS

In a series circuit, components ar e joined together in

a chain or series.

In a series circuit, there is only ONE path that

electr icity can follow. If th ere is a br eak a nywh ere in

the circuit, cur rent flow will be inter ru pted an d th e

circuit will stop work ing.

Exam ple: The circuit is a series circuit m ade u p of a

strin g of six light bu lbs. This is how Christm as t ree

lights used t o be wired.

Here is th e same circuit with a br eak (OPEN) in it.

Notice th at th e curren t can no longer flow from p oint

A to point B, and so the entire circuit will not work.

(That was th e trouble with wiring Christma s trees in

series. If one bu lb burn ed out, ALL th e lights would

go out becau se curr ent no longer could flow th rough

an y part of the circuit.)

When you look at wiring dia gra ms you will find ser ies

circuits in all sorts of shapes. For example, on the

circuits in th e next column tra ce th e path of cur rent

flow from p oint A to point B.

Notice that in each circuit there is only ONE path

that the electricity can follow. There are no places

where the current can bran ch into one path or a n-

oth er. Whenever you look at a circuit t ha t h as only

one path to follow, you are looking at a SERIES

circuit.

A B

A B

BREAK

A B

A B

A B

A B


8/206

P ARALLEL CIRCUITS

Often you will find circuits in which there is more

th an one pat h th at t he curren t can follow. As cur rent

flows from point A to point B it comes t o a bra nch, like

a fork in the r oad. When th is happens, the current

will flow thr ough all the bran ches at th e same t ime.

The amount of current that will flow through eachbranch depends on the resistances (loads) in the

bran ch. The part s of a circuit wh ere curren t is flowing

in two or m ore part s of th e circuit at t he sa me time is

called a parallel circuit.

In this circuit, you will notice that there are three

pat hs, or bran ches, th rough which cur rent can flow at

th e same t ime. This is a pa ra llel circuit.

Look at this circuit and count the number of paths

tha t current can flow at the sa me time. Three, right?

The voltage is the same across all branches in this

parallel circuit. This has the same effect as wiring

each bra nch directly to th e volta ge source.

Notice that like series circuits, the same parallel

circuit can be drawn in ma ny different ways.

A B

A B

A B

A B

A B


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SERIES-PARALLEL CIRCUITS

The series-parallel circuit is a combination of series

circuits a nd par allel circuits.

That par t of a circuit with in which ther e is only ONE

pat h for curr ent is a series circuit.

The part in which there is more than one path forcurr ent to follow is a pa ra llel circuit.

The part where current flows thr ough both one branch

and then through two or more branches is a series-

parallel circuit.

A B

SERIES PORTION

PARALLEL PORTION

SERIES-PARALLEL PORTION


10/20

AC THEORY

An alternating current AC continually changes in

potential-going from zero to maximum voltage and

back to zero. In add ition, AC periodically reverses it s

direction-from positive to negat ive. This is in contr ast

to a direct current DC, which maintains a steady

potential and flows in one direction only.

This graph shows how the voltage of an AC genera tor

chan ges. At point A the voltage is zero. Immedia tely

afterward it has a small, positive value. This valueincreases unt il it is maximum a t B. A moment lat er

the voltage, still positive, continues to drop steadily

un til it reaches zero again at C. Below C the voltage

becomes negative. Therefore, the voltage is shown

below th e zero line from C t o E.

Notice that the polarity does not reverse at B or D

th ese merely are th e point s of maximu m positive or

negative potential. The points of polar ity reversal ar e

at A, C, and E .

The complet e series of volta ge values, repr esent ed by

th e curve from A to E, r epres ent s one complet e cycle.When t he curve is cont inued, th e cycle is repeated.

The t ime n ecessary t o complete one full cycle is called

a period.

8

CHAP TER 2

ALTERNATING CURREN T

The n umber of cycles generat ed in one second deter-

mines th e frequen cy of th e AC voltage. Th e electr icity

supplied to most h omes is 60 hert z, which mean s the

volta ge goes t hr ough 60 complet e cycles from zero to

positive to zero to negative t o zero, in one second.

AC current can be transmitted more economically

over long dista nces tha n DC. This is one of th e great

advan ta ges of AC. It is easily tra nsform ed to higher

or lower voltages. This is a very desirable cha ra cter-

istic for radio and television circuit applications.

Man y types of motors a re designed for AC opera tion.

Some AC motors operate without brushes, which

elimina tes a comm on source of wear a nd some motor

maintenance problems.

Although AC does differ from DC in many ways,practically all the basic principles of electricity that

app ly to DC also apply t o AC.

0 0

ONE CYCLE

TIME

VOLTAG

E

A

B

C

D

E


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DC THEORY

An electric current is the motion of electrons. This

motion is called a current flow. To enable these

electr ons to flow and to confine them in a par ticularpath, an electrical circuit must be provided. (The

word circuit mean s t o go aroun d.) A complete elec-

trical circuit will provide a continuous p ath for th e

pas sage of cur ren t (electr on flow).

A practical electr ical circuit ha s a t least four pa rts: (1)

a source of electromotive force (emj), (2) a set of

cond uctors, (3) a load, a nd (4) a m ean s of cont rol.

Electromotive force (measu red in volts) is defined a s

th e force th at can m ove electrons. It can come from

a cell or ba tter y, a DC or AC generator, an electr onic

power su pply, or any equipment th at can provide a

CHAP TER 3

DIRECT CURREN T

differen ce of electr ical pr essu re.

Wires of many sizes can be used as conductors. The

ter m conductor actua lly refers to an y mat erial wh ich

offers low resista nce to current . Condu ctors m ay begood or poor; however, poor cond uctors will usu ally

be referred to as resistors or as insulators, if the

conductivity is very low. There are no sharp lines of

distinction which separa te condu ctors, resistors, an d

insulat ors. For insta nce, semiconductors fit into th e

ar eas between condu ctors an d resistors, and between

resistors and insulators.

The load of an electrical circuit may be any device

th at uses electr ical energy, such as a lamp, a bell or

buzzer, a toaster, a radio, or a motor. The load is

usually considered as being separate from the con-

ductors tha t conn ect it to a curren t source.

The curr ent flowing in a n electrical circuit is stopped

or started by means of switches. Further control is

provided by variable resistances, such as rheostats

and potentiometers. Fuses, circuit breakers, or re-

lays can be u sed as contr ols.

Many common electrical abbreviations are listed in

th e cha rt below.

Coulomb C Unit of electrical quantity. The number of electrons which must pass a point in one second to producea current of one ampere. The quantity which will deposit .0000116 ounce of copper from one plate to

the other in a copper sulfate solution.Ampere A or amp Unit of current. One coulomb flowing per second.Milliampere mA .001 ampere. (The prefix milli means one-thousandth.)Microampere A .000001 ampere. (The prefix micro means one-millionth.)Ohm ohm or Unit of resistance (R). Measure of the opposition offered to the flow of current. The resistance offered

by a column of mercury 106.3 centimeters in length and 1 square millimeter in cross-sectional area, at32 degrees Fahrenheit or 0 degrees Celsius.

Megohm M 1,000,000 ohms. (The prefix meg means million.)Microhm .000001 ohm. (The prefix micro means one-millionth.)Mho g Unit of conductance (g). Measure of the ease with which a conductor will permit current to flow. A

mho is the reciprocal of an ohm.Volt V Unit of pressure difference (emf-electromotive force). Pressure required to force one ampere of current

through a resistance of 1.Hertz Hz Frequency (one cycle per second.)Millivolt mV .001 volt. (The prefix milli means one-thousandth.)Microvolt V .000001 volt. (The prefix micro means one-millionth.)

Kilovolt kV 1000 volts. (The prefix kilo means one-thousand.)Watt W Unit of power. One watt is equal to one ampere of current under the pressure of one volt. The

formula for power is P = A X V.Milliwatt mW .001 watt. (The prefix milli means one-thousandth.)Kilowatt kW 1000 watts. (The prefix kilo means one-thousand.)Watt-hour Wh Unit of work. (Power X time.)Kilowatt-hour kWh 1000 watt-hours. (The prefix kilo means one-thousand.)Horsepower hp 746 watts. The power required to raise 550 lbs one foot in one sec.Farad F Unit of capacitance. Capacity of capacitors (condensers).Microfarad mfd or F .000001 farad. (The prefix micro means one-mil lionth.)Picofarad pF .000001 microfarad. (One-millionth of one-millionth of a farad.)Henry H Unit of inductance (L).Millihenry mH .001 henry. (The prefix milli means one-thousandth.)Microhenry H .000001 henry. (The prefix micro means one-millionth.)

UNITS SYMBOLS DESCRIPTION

2 3

4

2

2

1


12/2010

Now before we continue on with our study of basic

electricity, lets ta ke a look at the laws an d formu las.

... To aid you down the pat h to easier under sta nding

of th e laws an d formu las used in th e stu dy of Basic

Electricity, we will use the common name for the

term an d an a ppropriate initial. I know this isnt th e

way you would see these formu las in a ph ysics class

or an electrical engineering class, but in the real

world a volt is a volt an d sh ould be indicated by a V

in a formula not by an E for electromotive force.

OHMS LAW

The law which governs m ost electr ical ph enomena is

known as Oh ms law. It is the most importan t law in

electricity. In 1827, a German physicist, Dr. Georg

Simon Ohm (1787-1854), introduced the law whichbears his name. His many years of experimenting

with electricity brought out the fact that the a mount

of current which flowed in a circuit was directly

proport iona l to the applied voltage. In other words,

when the voltage increases, the current increases;

when t he voltage decreases, th e cur rent decreases.

If the voltage is held constan t, th e current will cha nge

as the resistance changes, but now in the opposite

direction. The cur rent will decrease a s th e resistan ce

increases, and then will increase as the resistance

decreases.

Ohm s law st at es: The cur ren t wh ich flows in a circuit

is directly proportional to the applied voltage and

inversely proportiona l to th e resista nce.

There a re t hr ee form ulas concerning Ohm s law a s

shown in th e mem ory circle.

Remember t hat a load is anything tha t u ses up some

of th e electr icity flowing t hr ough a circuit. A thin g to

remember also is, ELECTRICITY FOLLOWS THE

PATH OF LE AST RESISTANCE. In oth er words, it

is th e potent ial differen ce from one side of th e load t o

the other side th at forces curr ent to flow in a circuit.

Think about this, when was the last t ime you h eard

someone say my house is wired for 120 volts of

electromotive force. Okay, if we are going to say

volts lets u se a V for volt s in our form ula s. Let s

also us e R for r esista nce a nd A for am ps.

I hope this will help clear up some of the confusion

caused by unfamiliar initials in the formulas. The

cross reference chart shown below can be u sed as a

reference to terms; however, the int ent is t o keep the

formulas so under sta nda ble you wont ha ve to refer

back t o the chart.

IDENTIFICATIONMEASURED REFERRED TO IN USED

TERM IN FORMULAS AS IN THIS COURSE

Amperage Amperes (Amps) I A for ampsCurrent Amperes (Amps) I A for amps

Resistance Ohms or R R for resistanceVoltage Volts V or E V for volts

Electromotive Force Volts V or E V for volts

V(VOLTS)

A(AMPS)

R(RESISTANCE)


13/2011

Lets look a t a problem from t he p ersp ective of Ohms

law. First we need to understand the three factors

used in O hm s law:

1. Voltage is the difference in potent ial between two

point s or th e difference in sta tic cha nges between t wo

points, voltage does not flow or do any work in a

circuit, it is simply a potential. The fundam enta l law

to find voltage is stated:

The pressure in volts is equal to the current in

amperes multiplied by the resistance in ohms. The

equat ion is:

V (volts) = A (amps) X R (resistance)

2. Cur ren t is the flow of electr ons from a nega tive to

a positive potential. Without a difference in potential,

current will not flow. Curr ent is t he factor t ha t doesthe work in the circuit (light the light, ring the

buzzer). The fundamental law to find current is

stated:

The current in amperes is equal to the pressure in

volts divided by the r esistance in ohms. Th e equa tion

is :

3. Resista nce is the opposition to curr ent flow or th e

load. Curr ent t hr ough the resistor causes work t o be

done. The fundamental law to find resistance is

stated:

The resistance in ohms is equal to the pressure in

volts divided by the curr ent in amp eres. The equat ion

is :

Remember th at current is what does the work and it

only flows when there is a difference in potential.

In t his series circuit th ere is a difference in potential

between the positive and negative terminals of the

bat ter y of 20 volts DC.

Ther efore, curr ent will tr y to flow from th e negat ive

terminal to the positive terminal. There will be a

difference of potential across the resistor. The cur-

rent th rough th e resistor will be:

Usin g Ohm s law:

If we open t he switch, th e current in th e circuit goes

to zero becau se th ere is no pa th for curr ent to flow.

When we close th e switch, curr ent will aga in flow in

the circuit. There will be no voltage drop across the

switch because t here is n o resistance.

Now lets look a t h ow cur ren t flows in a par allelcircuit.

In t his case, the total resistan ce in th e para llel circuit

is figured using t he formu la:

A (am ps) =V (volts)

R (resistan ce)

R (resistance) =V (volts)

A (amps)

A =V

R= 1 amp

20VDC

20=

= RT or20 X 20

20 + 20= 10 ohm s

400

40=

R1 X R2

R1 + R2

BATTERY20VDC

A B

SWITCH

RESISTOR20

R120BATTERY

20VDC

R220

R310


14/2012

A =V

R3 + RT= 1 amp

20VDC

10 + 10=

The pa ra llel portion of th e circuit is equa l to 10 ohms.

The total curr ent in the circuit is equal to:

The voltage drop across the parallel portion of the

circuit will be:

V = A X RT = 1 a mp X 10 ohm s = 10 volts

But an int eresting thing happens Aen current r eaches

the parallel portion of the network. It now has two

differen t wa ys to go so it splits u p. To find t he cur ren t

in each leg, use Ohm's law:

Now lets chan ge the va lues of th e resist ors.

In t his case, the total resista nce in t he pa ra llel circuit

is figur ed using t he formu la:

The pa ra llel portion of th e circuit is equa l to 10 ohm s.

The total curren t in t he circuit is equal to:

The voltage drop across the parallel portion of the

circuit will be:

V = A X RT = 1 a mp X 10 ohm s = 10 volts

But an interesting thing happens when current

reaches the parallel portion of the network. It now

ha s two different ways to go, so it splits u p. Inst ead of

the .5 amp in each leg as before, we now get:

This shows that more current flows in the leg with

the least r esistance. Therefore, it seems th at curr ent

tak es the pat h of least resistan ce.

Lets look at what ha ppens wh en t he r esistance of oneof th e pa ra llel legs is zero.

In t his case, the total resistan ce in th e para llel circuit

is figured using t he formu la:

A =V

R1= .5 am p (Leg 1 or R1)

10V

20=

A =V

R2= .5 am p (Leg 2 or R2)

10V

20=

= RT or30 X 15

30 + 15= 10 ohms

450

45=

R1 X R2

R1 + R2

A =V

R3 + RT= 1 amp

20VDC

10 + 10=

A =V

R1= .33 am p (Leg 1 or R1)

10V

30=

A =V

R2= .66 am p (Leg 2 or R2)

10V

15=

= RT or20 X 0

20 + 0= 0 ohm s

0

20=

R1 X R2

R1 + R2

R130BATTERY

20VDC

R215

R310

BATTERY20VDC

R120

R20

R310


15/2013

The total curren t in t he circuit is equal to:

The voltage drop across the parallel leg 1 or R1 willbe :

V = A X RT = 2 a mps X 0 ohm s = 0 volts

Therefore, the current flow through leg 1 or R1 will

be :

With no curren t flow th rough t his leg, no work will be

done. Tha t is, th e light wont light or t he bu zzer wont

ring.

AMPERES

Current is measured in amperes. The term ampere

refers to the number of electrons passing a given

point in one second. This number is unbelievably

lar ge. If one could count th e individua l electr ons, he

would see app roximat ely 6,280 quadr illion electrons

go by during the one second that one ampere was

flowing.

This number of electrons, 6,280 quadrillion, is a

coulomb. This is a measurement of quantity (like

saying there are eight pints in a gallon of water).

When the electrons are moving, there is current.

Current can be measured in amperes, which is a

measurement of quantity multiplied by time. this

would be similar to saying th at we could fill so man y

gallon buckets with wat er at t he ra te of so ma ny pints

per minute.

One ampere is equal to one coulomb per second. An

instrument called an ammeterwill mea sur e electronflow in coulombs per second. The ammeter is cali-

brated in amperes, which we always use instead of

coulombs per second when speaking of the a mount of

current.

The schematic shows an ammeter connected in a

circuit to measure the current in amperes.

VOLTS

Electromotive force is measu red in volts. This is th e

amount of pressure difference between points in a

circuit. It is this pressure or difference of potentialtha t forces curren t t o flow in a circuit. For examp le,

suppose we ha ve two aut omobile tires, one inflated to

a pressu re of 30 poun ds per squa re inch, the other to

a pr essure of 10 pounds per squar e inch. If we conn ect

a hose to the valves of the tires, the difference in

pressur e will send air from th e 30-psi tire to th e 10-

psi tire. Air will continu e to flow un til th e pressu re is

the sam e in both tires.

One volt (potent ial differen ce) is requ ired t o force one

ampere of current through one ohm of resistance.

This is similar to a water pum p tha t forces wat er to

flow through a pipe. The water pump can be com-pared to the potential difference. The number of

pounds of pressure produced by the water pump

corresponds to the number of volts produced by a

current source. The action of the pump pushing a

nu mber of gallons of water per second past a certa in

point in a water system could be compared to the

action of a curr ent sour ce which sen ds a n um ber of

amperes of current. A valve in the pipe offers a

resistan ce to the flow of water ; the a mount of resis-

tance offered is comparable to the ohm. Keep this

water pu mp an alogy and th e road map ana logy in

mind a s you st udy electricity. It will help you t o bett er

understand the action of the Big Threevoltage,amper age, and r esistance in an electrical circuit.

A =V

R3 + RT= 2 amps

20VDC

10 + 0=

A =V

R 1= 0 amps

0V

20=

AMMETER

R1


16/2014

An inst ru ment t ha t will measur e voltage is known as

a voltmeter.

The schematic shows a voltmeter connected in the

circuit to measure the voltage. Voltmeter No. 1 is

connected to read the applied or source voltage.

Voltmeter No. 2 is connected to measu re t he voltage

drop, or potent ial differen ce, across R2.

OHMS

Resistance is measur ed in ohms. Resista nce opposes

th e flow of electrons (current ). So then the amoun t of

opposition to the flow is stated in ohms.

If a glass tu be 106.3 centimet ers (approxima tely 41

inches) in length and one square millimeter in a

crosssectional ar ea is filled with m ercury an d ma in-

tained at zero degrees Celsius (32 degrees Fahren-

heit ), th e tu be will offer a resist an ce of one ohm . This

is the stan dard by which t he ohm is determined.

An instru ment t hat will measure ohms is known as

an ohmm eter.

The schemat ic shows an ohmm eter conn ected to read

th e resistan ce of R1. The resistan ce of any ma terial

depends on the type, size, and temperature of the

material. Even the best conductor will offer some

opposition t o th e flow of electr ons.

VOLTMETER

R1

R2#1 #2

VOLTMETER

OHMMETER

R1

R2


17/2015

NOTES


18/2016

NOTES


19/20

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20/20

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Basic Electricity 1