Basic Electricity 4

8/8/2019 Basic Electricity 4

1/24

STUDY COURSEfor Home Appliances

HOW TO READ:

VOLT-OHM-MILLIAMMETER

TEST INSTRUMENTS

Module 4LIT 787742 Rev. B

BASIC ELECTRICITY


TEST LEADS


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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.

1


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TABLE of CONTENTS

PAGE

CHAP TER 1 ..............................................................................................3How to Read the Volt -Ohm-Mil liamme ter Test Instrume nt

*TES T ............................................................Se e Te s t Book LIT787743

*NOTE: We recomm end ta k ing the TEST for MODULE 4, r igh t

a fter s tud ying i t .

2


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CHAPTER 1

HOW TO READ THE


TEST INSTRUMENT

3

WHAT'S A VOM?

VOM is short for volt-ohm -milliamm eter . (VOMs a re

sometimes called mu ltimeters, because t hey do more

than one th ing.)

A typical VOM will allow you to measure voltage,

resistance, and current .

Voltage = electrical pressu re.

Resis tance = the a mount of resistan ce holding back

the flow of current (measured in ohms).

Current = the a moun t of electr icity flowing th rough

a wire or circuit component (measu red in a mperes).

There a re m an y different types an d bra nds of VOMs.

Some of th em a re sh own below. Now you can even bu y

a VOM th at will speak the r eading aloud. This is

ha ndy when you cant look at the m eter wh ile you a re

holding the test leads t o th e part you are test ing.

Though th ey look different , all VOMs do pret ty m uch

the same th ings.

Most VOMs will have th ese th ings:

1. Test leads These are the wires coming from

the meter t o the part being tested.

2. Meter scales and pointer (A digital displa y

on a digital meter) These show the amount of

whatever you are m easuring.

3. Funct ion switch This allows you to select

whet her you will be measu rin g A.C. or D.C. volts,

current , or resistan ce (ohm s).

4. Range se lector swi tch Allows you t o select

th e ran ge of values to be measu red.

On man y meters the function switch a nd th e ran ge

switch a re one an d th e sam e; you can select functions

and ranges with the one switch (as in the meter

pictur ed below).

Ther e ar e oth er min or differences between VOMs:On some th e test leads are perma nent ly att ached; on

other s you can rem ove th em. On some VOMs th ere is

a reset bu tt on, on oth ers th ere ma y be a fuse, and on

still other s th ere will be neither of these. Push ing the

reset but ton, or replacing the fuse, lets you rest art the

met er if you a ccident ally overload it.

In s pite of the differen ces, all VOMs ar e used in t he

same wa y to measu re voltage, cur rent , or resista nce.

TEST LEADS

SCALES

POINTER

FUNCTION/RANGE

SELECTORSWITCH


6/244

MEASU RIN G VOLTAGE

Volta ge is electr ical pr essu re. If you dont h ave t he

right a ir pressu re in your tires, you car wont r ide

right. If you dont ha ve the right electr ical pr essure in

an appliance, the appliance wont work right. (Most

Whirlpool app liances wan t 115-125 volts AC in order

to work right.) You can find out wheth er t he a pplianceis getting the r ight voltage by measur ing the voltage

at th e wall outlet (receptacle).

If an applian ce isn't getting th e proper voltage, nothing

else you do to fix it will help.

MAKING THE MEASUREMENT

When mea surin g voltage, these ar e the st eps you will

follow:

1. Attach the probes (another term for tes t l eads)

to the met er. Plug th e black probe into the outlet

marked negative. Plug the red probe into the

positive outlet.

2. Set the funct ion switch to AC VOLTS.

3. Select a ran ge tha t will include the voltage you

ar e measu ring. (Higher th an 125 volts AC if you

ar e measur ing 120 volts; higher th an 230 if you

ar e measu rin g 220 volts.) If you dont kn ow wha t

voltage to expect, use th e highest ra nge and t hen

switch to a lower r an ge if the voltage is within

tha t lower ran ge.

4. Touch the tips of the probes to the terminals of thepart to be measured.

5. Rea d th e s ca le.

6 . Decide what the reading means .

Making voltage m easur ement s is easy once you know

how to select a nd r ead th e scales on your meter. So

lets begin th ere.

SELECTING THE S CALES

There ar e severa l scales on your meter . To measu re

voltage in a ppliances you will use t he ones ma rkedACDC. (The sa me scales ar e used for both AC and DC

readings.) The one you use will depend on th e ran ge

an d fun ction youve set.

The n umber s on th e right side of the AC-DC scales

tell you what ra nges ar e available to you.

Example: This meter face has three scales for

measuring voltage. One is marked 10,

another 50, and the t hird is marked 250.

The scale you read is always determined by the

position of the range switch.

If the ra nge switch is set on 10V, you r ead t he 0-10

scale.

R x 1

1 VDC

2.5 V

10 V

25 V50A

100 V

250 V

500 V

R x 10

R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA


7/245

If the r an ge switch is set on 250V, you r ead t he 0-250

scale.

Notice tha t t he ra nge switch on th is meter is set on

500V.

Question: Which scale should you read?

Answer: Since there is no scale that actually says

500, you would read th e scale tha t sa ys 50,

an d then multiply your reading by ten (add

a zero to your reading).

Question: If the ra nge on th is meter is set on 25V,

which scale should you r ead?

Answer: Since there is no scale that actually says

25, you would read t he scale that says 250,

an d th en divide your reading by ten (drop

th e last zero from your r eading).

R x 1

1 VDC

2.5 V

10 V

25 V50A

100 V

250 V

500 V

R x 10

R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA

R x 1

1 VDC

2.5 V

10 V

25 V50A

100 V

250 V

500 V

R x 10

R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA

R x 1

1 VDC

2.5 V

10 V

25 V50A

100 V

250 V

500 V

R x 10

R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA


8/246

1. ________ Volt scale.

2. ________ Volt scale.

3. ________ Volt scale.

4. ________ Volt scale.

ANSWERS ON P AGE 8

LETS PRACTICE

Look at t he sett ing of the ra nge switch on th e examples 1 thr ough 4, an d th en list to the side which scale you

would rea d for ea ch ran ge shown.

R x 1

1 VDC

2.5 V

10 V

25 V50A

100 V

250 V

500 V

R x 10

R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA

R x 1

1 VDC

2.5 V

10 V

25 V50A

100 V

250 V

500 V

R x 10

R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA

R x 1

1 VDC

2.5 V

10 V

25 V50A

100 V

250 V

500 V

R x 10

R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA

R x 1

1 VDC

2.5 V

10 V

25 V50A

100 V

250 V

500 V

R x 10

R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA


9/247

READIN G THE AC VOLTAGE S CALE

When you read t he pointer position be sur e to read

the line mar ked AC.

The spaces on voltage scales are always equally

divided. The value of each space depends on which

ran ge you ar e using.

Example: When the range is set to 10V on this meter,

th e value of each spa ce on t he 0-10 scale is

.2 (two-ten th s) of a volt.

Example: When the range is set to 100V on this

meter, the value of each space is 2 volts.

Example: When the ra nge switch is set to 1000V on

this meter, the value of each space is

20 volts.

NOTE: When the pointer st ops between mar ks, just

read th e value of the near est mark .

Example: The pointer on th is meter face is between

115 and 120 volts on the 250 volt scale.

Read it as 120 volts. You wont gain an y-

th ing by trying to read t he volta ge exactly.

Example: The pointer on this meter is between 35

an d 36 volts on t he 50 volt scale. Read it a s

36 volts. The differen ce between 35.5 and

36 isnt worth both ering about.

R x 1

1 VDC

2.5 V

10 V

25 V

50A

100 V

250 V

500 V

R x 10

R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA

R x 1

1 VDC

2.5 V

10 V

25 V

50A

100 V

250 V

500 V

R x 10

R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA

R x 1

1 VDC

2.5 V

10 V

25 V

50A

100 V

250 V

1000 V

R x 10

R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA

2 VOLTS 10 VOLTS

20 VOLTS 100 VOLTS

.2 VOLT1 VOLT


10/248

SELF-CHECK

ANSWERS FROM PAGE 6

Read t he 50-volt scale ad d a final

zero for the reading.

1.

2.

3.

4.

Read t he 250-volt scale.

Read the 250-volt scale drop the

last zero for the r eading.

Read t he 10-volt scale ad d a final

zero for the reading.

R x 1

1 VDC

2.5 V

10 V

25 V

50A

100 V

250 V

500 V

R x 10

R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA

R x 1

1 VDC

2.5 V

10 V

25 V

50A

100 V

250 V

500 V

R x 10

R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA

R x 11 VDC

2.5 V

10 V

25 V

50A

100 V

250 V

500 V

R x 10R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA

R x 1

1 VDC

2.5 V

10 V

25 V

50A

100 V

250 V

500 V

R x 10

R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA


11/249

1. ________ Volts.

2. ________ Volts.

3. ________ Volts.

4. ________ Volts.

ANSWERS ON P AGE 10

LETS P RACTICE AGAIN

Look at t he met ers below. Write the rea ding in th e space provided. NOTE: Be sure t o look at t he ra nge switch

first so tha t you will read t he correct scale.

R x 11 VDC

2.5 V

10 V

25 V50A

100 V

250 V

500 V

R x 10R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA

R x 1

1 VDC

2.5 V

10 V

25 V50A

100 V

250 V

500 V

R x 10

R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA

R x 1

1 VDC

2.5 V

10 V

25 V50A

100 V

250 V

500 V

R x 10

R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA

R x 1

1 VDC

2.5 V

10 V

25 V50A

100 V

250 V

500 V

R x 10

R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA


12/2410

SELF-CHECK

ANSWERS FROM PAGE 9

7 Volts.

1.

2.

3.

4.

75 Volts.

100 Volts.

120 Volts.

R x 1

1 VDC

2.5 V

10 V

25 V

50A

100 V

250 V

500 V

R x 10

R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA

R x 1

1 VDC

2.5 V

10 V

25 V

50A

100 V

250 V

500 V

R x 10

R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA

R x 1

1 VDC

2.5 V

10 V

25 V

50A

100 V

250 V

500 V

R x 10

R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA

R x 1

1 VDC

2.5 V

10 V

25 V

50A

100 V

250 V

500 V

R x 10

R x 1

R x 100

R x 1K

R x 10K

0.5 mA

5 mAAMPS

50 mA


13/2411

MEASUR ING LINE VOLTAGE

Now that you kn ow how to select t he scales and r ead

th e meter , youre rea dy to learn how to ma ke

measurements with it. First, how to measure line

voltage. This is the first an d most import an t par t of

checking out an appliance tha t does not operat e.

Line voltage is the voltage coming from the wall

outlet.

There sh ould be approxima tely 120 volts AC at the

outlet under no loadconditions.

No load m eans tha t n o applian ce is conn ected, or tha t

an appliance is conn ected bu t is t ur ned off.

To measure l ine voltage -no load:

1. Set meter to measure AC volt s .

2. Set range selector to range nearest to, but higher

th an , 120 volts.

3. Inser t e i ther test lead into one s lot of an empty

wall receptacle.

4. Inser t the other test lead into the other s lot of the

sam e outlet. (Disregard t he center hole for this

test).

5. Read the meter . The reading should be between

115 and 120.

NOTE: Most a ppliances ar e ra ted 120V, but will work

on voltages r an ging from 110 t o 125.

To meas ure l ine voltage-under load:

1. Make sure that (a) an appl iance is plugged in to

one of the receptacles an d th at (b) the applian ce

is turn ed on.

2. Follow steps 1 through 5 for no load conditions,

inserting your test leads int o the empty r eceptacle

next t o the one into which t he ap pliance is plugged.

3. Under load conditions (appliance is turned on),

your readin g will be slightly less th an un der n o-

load condit ions.

Note: Appliances with heavy dr ive motors, such a s

au tomatic washers an d dishwasher s, should also be

tested at the moment of start. If the voltage drops

more tha n 10% of volta ge when th e motor is sta rt ed,

it means that there is a problem with the electrical

sup ply (th e electr icity coming in to th e recepta cle).

TESTING FOR GROUND AND P OLARITY

Ground

A ground is a voltage reference point.

If a component is grounded (connected) to a chassis

(th e meta l fra me on which components are m ounted),

i t means that there is no vol tage between the

component an d the chassis.

If a chassis is grounded to the ear th, i t mean s tha t

ther e is no voltage between the chassis and t he eart h.

If there is voltage between a chassis and the earth,think of it as voltage on the loose. Its dangerous. If

you stand on the earth and touch the chassis, the

voltage will cause electricity to flow through your

body. Or t hr ough th e cust omers body. Bad n ews

either wa y! So it is importan t t o make sure th at the

out lets into which your a ppliances are plugged have

been corr ectly wired. Tha t will protect th e user s from

electr ical shock.

You do tha t by checking for ground a nd polar ity.


14/2412

Polarity

If an outlet is wired backwards , tha t is, if th e hot wire

is conn ected t o the long slot of th e outlet, th e app lian ces

conn ected t o that outlet ma y be unsa fe to operat e or

blow th e fuse or t rip th e circuit brea ker.

To test for ground:

1. First , test for l ine voltage. (If there is no voltage

you can t t est for groun d.)

2. Notice that the receptacle has a longer and a

shorter slot. If th e outlet h as been mount ed right

side up, t he longer slot will be on t he left.

3. Test for vol tage between the short s lot and th e

groun d recepta cle (th e roun d hole). If th ere is line

voltage between these two points it means that

th e receptacle is grounded.

4. If there is no round hole (ground receptacle),

touch one of your probes to the screw th at fast ens

th e coverplate t o the outlet.

To test for polarity:

1. Test to make sure that there is l ine vol tage

between th e longer an d shorter slots.

2. Test to make sure there is l ine vol tage between

th e short slot an d the center screw or th e round

hole (groun d r eceptacle).

3. Test to make sure there is NO VOLTAGE between

th e longer slot an d the center screw or the round

hole (groun d r eceptacle).

If these th ree tests dont work out t his way, th e outlet

is incorrectly wired and should be corrected by a

licensed electr ician .

GROUND SCREW

GROUND (COPPER WIRE)

NEUTRAL SIDE(White wire tosilver screw)

HOT SIDE

(Black wire toBrass screw)

120 VOLTS

120 VOLTS

120 VOLTS

120 VOLTS

120 VOLTS

ZERO VOLTS

ZERO VOLTS


15/24

13

MEASURING RES ISTANCE (OHMS)

Electrical appliances will not work u nless th ere is a

complete path around which electricity can flow. As

you know, a complete path is called a circuit.

If there is a break in th e circuit, th e appliance wont

work.

Sometimes we deliberately break the circuit. For

example, when we tur n a switch t o its OF F position,

we int err upt th e flow of electricity. (Its just like

breaking a wire in two, except m ore elegant.)

When there is a complete path we say we have

continuity in the circuit. When we test to find out

whether th ere is a break in the path , we say we are

mak ing a cont inuity check.

How? Cont inuity checks are made by measur ing the

am ount of resist an ce ther e is to the flow of electr icity.

If there is so much resistance that it is too high tomeasu re (called infinite), then we say tha t th e circuit

is OPEN (th ere is no complete pat h for t he electricity

to follow).

Infinite resistance = open circuit

If there is no measurable resistance to the flow of

electr icity, we say we have a n open circuit or infinit e

resistan ce between the t wo point s being measured.

Some m easurable or zero resistance = continuity

If there is SOME resistance, it means that there is

cont inuity, but t ha t t here is also one or more loads on

the line a light, a motor, etc.

NOTE: A load is an electr ical component tha t u ses

electr icity to work : e.g., a light bu lb, a motor, a hea ter

coil.

If there is NO resista nce between t he two point s, it

means the electricity is flowing directly from one

point t o th e oth er.

Example: In th e circuit below, the curr ent would

flow directly from point C to point D,

without flowing through load X.

If we wanted current to flow from point C to D, we

would say we ha d cont inu ity. But if we DIDNT wan tit t o flow from point C t o D, tha t is, if it flowed from

C to D by accident or err or, then we say we ha ve a

short circuit, or short.

Unwan ted cont inui ty = short c ircui t

Exam ple: In t he circuit below, point X is conn ected to

eart h ground. This is the same as conn ect-

ing it to point B, and so current would

flow through loads R and S, and then

directly to ground .

When t his ha ppens by accident, we say th e circuit is

shorted to groun d, or we m ight just sa y the circuit is

shorted.

A B

S

T

XR

A B

C

D

X


16/2414

SETTING UP THE METER

Measur ing ohms (th e unit of measure for r esistance)

i s l i k e m e a s u r i n g v o l t a g e , e x c e p t t h a t t h e

measurements a re always made with t he power turn ed

OFF . Why? Becau se when youre m easur ing ohms,

youve set your m eter to measu re t he continuity of a

circuit , NOT th e qua nt ity of curr ent . If you jolt yourmet er wit h a shot of electrical power when its set for

ohms, youll dest roy it.

Lets look a t t he st eps one at a t ime.

1. Attach th e lead s to the m eter.

Plug the black lead into the negative outlet, the

red lead into th e positive out let.

2. S et the function switch on OHMS .

3. Set the range.

The r an ge selector switch will always ha ve severa l

ran ges, of resista nce (ohms) measur ement s. Theran ges are shown like this:

Rx1: The actual resistance reading shown on

th e meter face, times 1

Rx10: The resistance reading, times ten; add

one zero to the readin g

Rx100: The resista nce reading, times 100; add

two zeros to the rea ding

Rx1K: The r esistance read ing, times 1000; add

th ree zeros to th e reading (K means 1000).

Set th e ran ge so it is higher t ha n th e resistan ce you

expect. If you dont k now what meas ur ement to expect,

use the highest setting and adjust downward to a

rea ding of less th an 50. The left side of th e scale is too

crowded for an accur at e reading.

4. Zero the meter.

There is a small battery inside the meter that is

used to supply power to t he meter only when

th e OHMS fun ction is used. Because th e batt ery

voltage changes slightly with each use, you should

zero th e m etereach time you set th e meter or

use a different scale to measu re ohms.

Tozero th e metermeans t o adjust t he pointer so tha t

it reads ZERO ohms when the two test leads are

touched together .

Her es h ow tozero th e meter.

1. Touch th e tips of th e leads together . (Dont h old

th em with your fingers).

2. Use the Ohms adjust knob on th e front of the VOM

to line up th e pointer over the zero on t he OHMS

scale.

NOTE: If the met er will not zero i t means that thebatt ery in the VOM is weak a nd sh ould be replaced.

5. Testing.

Touch each pr obe to the pa rt or the portion of the

circuit you a re mea sur ing.

Example: If you are measuring the cont inuity of a

load such as a light bulb (or any other

load you could easily r emove), touch one

test lead to the meta l screw, and an other

to th e bottom of the bu lb (or load). If your

meter sh ows infinite resistan ce it mean s

that the filament in the light bulb is

broken, and you have an OPEN (a break)

circuit.

Example: If you ar e measuring cont inuity in a load

that cannot be easily removed, (1) dis-

connect one wire from th e load, a nd then

(2) touch your test leads t o the term inals

where th e line voltage wires are at tached

to the load.

1 VDC

2.5 V

10 V

25 V50A

100 V

250 V

500 V

R x 10

R x 1

R x 100

R x 1K

0.5 mA

5 mAAMPS

50 mA

R x 10K


17/24

15

6. Read the OHMS scale.

Scale direction. Youll notice th at th e OHMS scale

is a little screwy.

All the other scales ha ve their highest nu mbers to the

right, but the OHMS scale almost always has the

ZERO on th e right a nd infinite resistance to the left.

Seems ba ckwar ds, doesnt it?

Try th inking of it like this. When r esistance is zero,more cur rent can flow th rough th e circuit t ha n when

resis tance is higher than zero. The higher the

resistan ce, th e less electricity t ha t can flow. In other

words, an ohmmeter actually senses the amount of

current flow.

So, just as th e highest voltages are shown at t he right

of the scale, the highest possible current flow (zero

resistan ce) is also shown a t t he right .

Whether it mak es sense or not, that s the wa y it is.

The OHMS s cale is read opposite to the wa y you r ead

th e AC-DC scales.

Un even divisions. Th eres an other d ifference.

As you know, the ma rks on AC-DC scales are equally

spaced. But a s you move from right to left on t he ohms

scale the size of the spaces gets smaller and the

numbers get bigger (the scale is compressed).

The highest reading you get is cal led inf ini te

resistance.

This means th at r esistance is so high that curr ent

cann ot flow (in oth er words, t her e is an open circuit).

When t he pointer is at t he h igh (left) end youll have

to estimate (guess) at th e reading. This is no problem,

becau se the differences in r esistance at t he high endsdont ma tt er mu ch.

Example: If a reading shows high resistance when

th ere is sup posed to be ZERO resista nce, it

doesnt ma tter if th at high resistan ce is 5

thousand ohms or 5 million ohms. Either

way, it mean s you h ave a pr oblem.


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16

1. Reading: ________

2. Reading: ________

3. Reading: ________

4. Reading: ________

ANSWERS ON P AGE 19

NOW LETS P RACTICE AGAIN

Look at t he m eters below. Write the r eading in th e space provided. NOTE: Be sure t o look at th e ran ge setting

before you read the scale, and remem ber to add zeros to your reading.

R x 10

R x 1

R x 100

R x 1K

R x 10K

R x 10

R x 1

R x 100

R x 1K

R x 10K

R x 10

R x 1

R x 100

R x 1K

R x 10K

R x 10

R x 1

R x 100

R x 1K

R x 10K


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5. Reading: ________

6. Reading: ________

7 Reading: ________

8. Reading: ________

17

R x 10

R x 1

R x 100

R x 1K

R x 10K

R x 10

R x 1

R x 100

R x 1K

R x 10K

R x 10

R x 1

R x 100

R x 1K

R x 10K

R x 10

R x 1

R x 100

R x 1K

R x 10K

ANSWERS ON P AGE 20


20/2418

SELF-CHECK

ANSWERS FROM PAGE 16

20 Ohms.

1.

2.

3.

4.

500 Ohms.

700 Ohms.

Infinate

resistance

R x 10

R x 1

R x 100

R x 1K

R x 10K

R x 10

R x 1

R x 100

R x 1K

R x 10K

R x 10

R x 1

R x 100

R x 1K

R x 10K

R x 10

R x 1

R x 100

R x 1K

R x 10K


21/2419

SELF-CHECK

ANSWERS FROM PAGE 17

400 Ohms.

5.

6.

7.

8.

1000 Ohms.

15000 Ohms.

5 Ohms.

R x 10R x 1

R x 100

R x 1K

R x 10K

R x 10

R x 1

R x 100

R x 1K

R x 10K

R x 10

R x 1

R x 100

R x 1K

R x 10K

R x 10

R x 1

R x 100

R x 1K

R x 10K


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LETS REVIEW WHAT THE TERMS AND MEASUR EMENTS MEAN

INFINITEresistan ce mean s open circuit.

ZERO resistan ce mean s contin uity or a possible short .

INFINITE RES ISTANCE mean s a br eak in t he circuit or you h ave picked th e wrong scale.

CURRENTis like a car t raveling on h ighways or roads. If the road ha s a bridge opened or washed out t he car

cann ot get thr ough.

Its th e sam e with CIRCUITS . If th ere is a br eak (infinite res ista nce), th e curr ent will not flow (open circuit).

OPEN CIRCUITS ar e usu ally cau sed by wires tha t h ave come loose from a term inal, by broken wires, or by a

conn ection th at ha s been incorr ectly soldered.

ZERO RES ISTANCEmean s th ere is continuity or a possible short.

ELECTRICITYwill follow the path of least resistance. When there is a path of ZERO resistance all the

electricity (cur rent ) will flow th rough th at pat h, instea d of thr ough the loads tha t m ake t he app lian ces work.

A REA DING OF ZER O OHMS across a component mean s th at th e electricity doesnt h ave to do an y work while

flowing thr ough the component . Its as t hough th e cur rent ha s a wide empty h ighway to flow thr ough.

SH O RTS ar e usua lly cau sed by a component tha t is accidentally groun ded, or by wires tha t a re touching other

wires or groun d.


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Basic Electricity 4

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