Chapter 22-23 Review
ANT
Name
~Il Z.
1. a. Where do the electrons come from that produc heat and light in a bulb? -f/&lt1
b. Does voltage flow through a circuit, or is voltag established acro
circuit?
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c. What is Ohm's Law?
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d. Why are thick wires rather than thin wires used to carry large currents?
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2. a. What has a greater resistance, a~o-watj»r
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a lSO-watt bulb?
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b. If three lamps of equal resistance are connected in parallel to a 6-voit battery, how many
PALALL!
volts are across each lamp?
c. Why does the Wtal circuit Tistanre
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1/::: 120v
tit
it ...
connected to a 120-Voutlet.
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3 a. What is a short circuit? LUl-ttlJ TI1~ C/J.(2Il.!ttJ 7 i=l.OlJ.J!
~ t:s. ~"'A,NLl!'
b. What's the purpose of a fuse or circuit breaker?
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6V
decreas1 when resistors are added in parallel?
d. Calculate the current in a l40:W electntblanRet
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c. What's the current in a l4-ohm t9aster when~"t'
eo to a l20-volt circuit? "Ii! t.ulr
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d. Calculate the resistance oTthe filamenUff"tJig
t carries 0.4 A when 3.0V is
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impressed across it.
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4. a. Calculate the equivalent resistance of this circuit.
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b. What is the current in one of the ten-ohm resistors?
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20V
5. a. Calculate 'went
resistance of this circuit.
b. What's the ~n
the circuit?llv'
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c. Calculate the voltage dr<fP
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across the three-ohm resistor.
d. What resister consumes the
most power? The least?
e. = ~
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6. a. Calculate the equivalent resistance of this
1'2 .S.sz-
circuit.
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b. What's the. total cu~rfnt iQ the circuit?
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c. What is thfpower
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Batteries and Direct Current
1) The net direction in which electrons flow through a circuit is:
(a) the direction of the conventional current.
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(b) opposite the conventional current.
Answer: (b)
Oiff:/
---
50
Answer: B
Oift:1
Current and Drift Velocity
iA
Answer: B
Diff:1
Answer: C
Dif/: 1
Resistance and Ohm's Law
6) Consider a current moving from left to right through a resistor. Which end of the resistor is at higher
potent~ial?
Ie
ight
C) indeterminate, depends if current is charging a battery or discharging a battery
Answer: A
Dift: 2
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Answer: C
Dilt" 1
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18) Consider two copper wires. One has twice the length and twice the cross-sectional area of the
other. How do the resistances of these two wires compare?
Both wires have the same resistance.
B)
ance of the shorter wire.
C) The longer wire has four times the resistance of the shorter wire.
D) The shorter wire has four times the resistance of the longer wire.
E) The shorter wire has twice the resistance of the longer wire.
Answer: A
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20) A device obeying Ohm's law must have a resistance which
A) is proportional to voltage.
B i
ional to current.
) is constant.
•
Answer: C
Diff:/
22) A potential difference (V) is applied to the ends of an object causing a current (I) to flow through it
If the object obeys Ohm's law we can obtain the resistance by
A) multiplying current by voltage.
B) dividing current by voltage.
C) calculatin 12V.
IVI mg voltage by curren.
Answer: D
Diff:/
24) What potential difference is required to cause 2.0 A to flow through a resistance of 8.00?
Answer: 16'v
Diff: 2
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25) Electr'
. tance has units of
A) ohms.
mperes.
~
C) volt-amperes.
~ 'D) O-m.
E) (O-m) -1.
Answer: A
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17.4 ElectricPower
1) If the resistance in a constant voltage circuit is doubled, the power dissipated by that circuit will
A) increase by a factor of four.
B) decrease to one-fourth its ori inal value.
decrease to one-half its original value.
D) Increase y a ac or 0
o.
E) be unchanged.
Answer: C
Oiff:2
2) A home appliance is rated at 250. watts connected to 120. V.
(a) What current does it draw?
(b) What is its resistance?
)Pr11ow many kw-h does i~use in one 24-hour day?
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Answer: (a) 2.08 A
(b) 57.60
(c) 6.00 kw-h
Oiff: 3
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Answer: D
Oiff: 1
4) Consider a 1.40kW hair dryer operated on 120. v. What is
(a) ~he cu.rrent?
(b) Its resistance?
Answer: (a) 11.7A
(b) 10.30
Oiff: 3
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8) Appliances in the USA are designed to work on 110-120 V, whereas appliance
urope operate
on 220-240 V. What would happen if you tried to use a European electric shaver in this country?
A) It would probably work as well as it does in Europe, since it is the power rating, not the
voltage rating, that mailers.
B) It would probably work as well as it does in Europe, since it is the current rating, not the
.
.
,
volt
C) It would barely work (or maybe not work at all), since the voltage here is too low to push
nough current through the device.
and bum up before very long.
E) This question cannot be answered without knowing the frequency used in Europe and in the
USA, since this is the parameter that mailers most in any electrical device that operates on alternating
current.
Answer: C
Oift: 2
14) A 200. a resistor is rated at 1/4W.
(a) What is the maximum current it can draw?
(b) What is the maximum voltage that should be applied across it?
Answer: (a) 3.54 mA
(b) 7.07 V
Oift: 3
15) Electric power has units of
A) ohms.
B) a-m.
C) amperes.
Cll:icilt-amperes
(watt)
Ej1n-m) -'.
I
Answer: 0
Oift:1
16) A lamp uses a 150.W bulb. If it is used at 120. V, what current does it draw and what is its
resistance?
Answer: 1.25 A; 96.0
Dift:2
a
17) In the graph shown, what physical quantity does the slope represent?
p
(W)
A)
B)
C)
0)
E)
current
energy
resistivity
conductivity
resistance
v (wob)
Answer: A
Diff: 2
18) A 500-W device is connected to a 100-V power source. What current flows through this source?
A) 50,000A
B) 200. rn
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=(60V
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E) 1.60 x 1018electrons/s
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Answer: C
Diff:2
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Resistances in Series, Parallel, and Series-Parallel Combinations
18.1 Resistances in Series, Parallel, and Series-Parallel Combinations
1) This is a symbol for which of the following?
Answer: B
Diff: 1
2) In 5.0 minutes, 500. Coulombs pass through a 24. ohm resistor. What is th
resistor?
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A) 300. V
~
lCf30.v
D) 400. V
E) 35. V
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Answer: B
3) R1
potential across the
= 6.0 volts
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For this circuit find:
(a) the total resistance connected to the battery.
(b) the current in each resistor.
Answer: (a) 9.6 0
(b) 11 0.63 A, 12= 0.45 A, 13= 0.18 A
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8) An air conditioner uses 2000. watts at 120. volts. What is its current and resistance?
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Answer: 16.7 amperes and 7.20 ohms
Oift: 2
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9) Why does a lamp burn out quicker if it is turned on and off many times, rather
burning?
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V
a one that IS left
!
Answer: The Tungsten filament has a positive temperature coefficient of resistance. Thus when it is
first turned on, its current is excessive and the filament for an instant evaporates some of its surface,
thereby becoming thinner.
Oift:2
10) Two resistors in series equal 9.0 ohms total; but the same two resistors in parallel are equivalent
to 2.0 ohms. What are the resistor values?
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Answer: 3.0 and 6.0 ohms
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11) In order for the human body to conduct 100. mA or more, connected to 120. volts, its resistance
would have to be less than what?
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Answer: 1.20 kQ
Dift: 2
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13) What resistance added to 633. Q in parallel would produce an equivalent 205. Q?
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Answer: 303. Q
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15) My hair dryer is rated at 1500. watts and my television only uses 100. watts, so why do I pay
more for electricity for my TV than for my hair dryer in a year?
~
Answer: One pays for energy, not power. I use my TV so much longer that its energy usage (power X
time) is more than the hair dryer.
-----------DifJ: 2
16) A 3. Q resistor is connected in parallel with a 6. Q resistor. This pair is then connected in series
with a 4. Q resistor. These resistors are connected to a battery. What will happen if the 3. Q resistor
burns out, i.e., becomes an infinite resistance?
A) The current in the 4. Q resistor will drop to zero.
The curren In e.
resls or WlllTnC~
e current provide
yea
.
c ange.
D) The power dissipated in the circuit will increase.
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Answer: B
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17) A metal wire conductor would pass less currr~ if its
A) length were decreased.
tJ6T
B) cross-sectional area were larger.
con uctlvit were sma I er.
eSls Ivity were smaller.
-
7
Answer: C
Diff:2
18) One terminal of a battery is connected to a closed circuit, while the other terminal is left
unconnected. Which of the following statements is true?
(Al No current flows through the batte!V..J:lru:L1hap.o.tentialof any point in the circuit is the same.
B) No current flows tlirough tfie battery, and the potentials of different points iiiltTe-eif
.
different.
C) Current flows through the battery, and the potential of any point in the circuit is unchanged.
D) Current flows through the battery, and the potentials of different points in the circuit are
different.
Answer: A
Dift:2
Answer: C
Oift: 2
23) In the water flow analogy, the height of the water is analogous to what electrical quantity? Also a
pump is analogous to what?
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V
Answer: potential (voltage); a battery (or emf)
Oift3
24) When resistors are connected in parallel, we can be certain that
A) the same current flows in each one.
caDfie potential difference across eaCh ISthe same;::::>
(101
C) the power dlsslpatea in each ISthe same.
---D) their equivalent resistance is greater than the resistance of anyone of the individual
resistances.
tz;1=.
Answer: B
Oift 1
25) A 3.0 0 resistor is connected in parallel with a 6.0 0 resistor. This combination is connected in
series with a 4.0 0 resistor. The resistors are connected to a 12. volt battery. How much power is
dissipated in the 3.0 0 resistor?
A) 12 W
B) 5.3 W
~ 0(
6"
C) 7.7 W
e,X'1IYJ,
O)6W
E) 2.7 W
Answer: B
Oiff:2
27) Two 4. 0 resistors are connected in parallel, and this combination is connected in series with 3 O.
What is the effective resistance of this combination~
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0) 1.20
E) 4.0
'-> tg,... eA 12e
Answer: B
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28) Two 100W light bulbs are to be connected to a 120V source. What is the current, potential
difference, and dissipated power for each when they are connected:
(a) in parallel (the normal arrangement)?
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Answer: (a) 0.83 A in each; 120 V; 100Weach, 200W total.
.
(b) 0.42 A in each; 60 V; 25W each, 50W total.
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29) A combination of 2.0 0 in series with 4.0 0 is connected in parallel with 3.0 O. What is the
equivalent resistance?
Answer: 2.0 0
Oiff: 2
30) Four 20. 0 resistors are connected in parallel. What is the equivalent resistance?
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31) The lamps in a string of holiday lights are connected in parallel. What happens if one lamp bum
out? (Assume negligible resistance in the wires leading to the lamps.)
A) The
e
C) The
0) The
E) The
bri btness of the.lamps-will not change appreciably.
other lamps get dimmer eqoatl .
other lamps get brighter equally.
other lamps get brighter, but some get brighter than others.
other lamps get dimmer, but some get dimmer than others.
Answer: A
Oiff:2
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32) As more resistors are added in parallel to a constant voltage-source, the power supplied by the
D
source
r = I') K..
A) increases.
B ecreases.
does not change.
0) increases for a time and then starts to decrease.
e)
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Answer: A
Oift 2
34) As more resistors are added in series to a constant voltage source (zero internal resistance), the
power supplied by the source
~es-ne
ange.
~eases.
C) in
0) increases for a time and then starts to decrease.
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c ttl!t}.st!~
it-a IS,!7-lNCt
.
Answer: B
Oift: 2
n and a 12.
by the 6.0
resistor?
A) 48.W
B) 12.W
35) A 6.0
n
n resistor
are connected in parallel to a 36. V battery. What power is dissipated
n resistor
are connected in series to a 36. V battery. What power is dissipated
C) 486'w
~~~
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Answer: E
Oift: 2
n and a
36) A 6.0
12.
by the 6.0
resistor?
A) 216'w
n
'4."1"
B) 486'w
.
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Answer: 0
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8.W
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38) Three identical resistors are connected in parallel to a 12.V battery. What is the voltage of any
one of the resistors?
A) 36. V
~ Ci'l'~U e
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~
E) 3. V
it ~
SCiwtQ
f2. V
Answer: C
Oift 1
39) When two or more resistors are connected in series to a battery
~
A) the total voltage across the combination is the algebraic sum of the voltages across the
. dividual r s'sto
B) the el'i~lent
resistance of the combination is equal to the sum of the resistances of ea
resistor.
u.619Jhe_same current flows through each resistor.
0) all of the other choices are true.
AA
.
Answer: 0
Oift:2
40) Three identical resistors are connected in series to a 12-V battery. What is the voltage across
anyone of the resistors?
A)
B)
C)
0)
E)
12 V
3V
36 V
0V
4V
Answer: E
Oirl: 2
.
Answer: B
Oift: 1
42) Three identical resistors are connected in series to a battery. If the current of 12 A flows from the
battery, how much current flows through anyone of the resistors?
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Answer: A
Oift: 1
43) If entical resistors re connected in parallel, and a battery is connected as shown, which resistor
will have e a
s current flowing through it?
A) middle resistor
B) resistor closest to the battery
C re .s10 fartbes o.Jbe.batle
none, currents are the same
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Answer: D
Diff:J
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44) When two or more resistors are connected in parallel to a battery
A) the voltage across each resistor is the same. T('tu.~
B) the total current flowjng from the battery eq~als the sum of the currents flowing through
each resistor.
,(lUI!' L~fL.QM,. (HI'\C) the equivalent resistance of the combination is less than the resistance of anyone of the
I'" (.)
\t\Lu.~
resistors.
D) all of the other choices are true.
Answer: D
Dift: 2
Diff: 2
12) This is the symbol for a
A) ground.
B) switch.
C) fuse.
D) capacitor.
E) resistor.
Answer: B
Diff:1
-
13) This is the symbol for a
A) battery.
B) resistor.
C) capacitor.
D) fuse.
E) switch.
Answer: C
Oiff: 1
1 ) This is a symbol for which of the following?
A) galvanometer
B) voltmeter
C) resistor
CJ?~~e~
Answer: E
Oiff:1
2) A current reading is ob ined by properly placing an ammeter in a circuit consisting of one resistor
and one battery. As a result
A) the voltage drop across the esistor increases.
~ 0
BJJbe-GurrenHlowinginihe-Gir'
increas.es
the current flowing in the circuit
creases.
D) the current oWing In the circuit'do
no change.
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Answer: C
Oiff: 2
10) This is a symbol for which of the following?
A) galvanometer
B) voltmeter
C) ammeter
D) fuse
E) ground
Answer: B
DiJf: 1
Answer: 0
DiJf:I
18.5 Household Circuits and Electrical Safety
2) When double-checking a wire which is assumed to be not "hot", you might see an electrician
"testing" for electricity by briefly touching the suspicious wire WITH THE BACK OF THE HAND. Why
do you suppose the front of the fingers are not used?
Answer: If current flows through the fingers the muscles are likely to contract. If the front of the
hand were used then the hand might be clamped to the wire, but using the back of the
hand prevents this worsening of the situation.
Diff: 3
~OpA.
8) The usual household fuse or circuit breaker is rated at
15 A.
D) 20 mAo
E) 200 A.
Answer: B
Oiffl
10) Why aren't houses wired with outlets in series instead of in parallel?
Answer: Unless all circuits were being used, none would operate. Also all would have to use the
s~me current.
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11 ) My electric razor operates on 120. V and requires 3."0Amperes. How much current comes out
after delivering 360. walts of power?
A) 120/3.0 A
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4-
B) O.A
~
E) 2.4 A
Answer: C
Diff: 1
17) This is a symbol for which of the following?
A)
B)
C)
D)
E)
resistor
ammeter
voltmeter
fuse
galvanometer
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Answer: D
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3rd wire on a 3 prong plug is connected to
TO
Answer: A
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E:.,,«(..CS.s
CftARG Cr
Answer: C
Ojf/: 1
Go TO
life. eA~TH
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19) A "blown" fuse has
A) moderate resistance.
B zero ~istal'l .
C) in mire (very large) resistance.
to
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Pl.-OW () F
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