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Name: ________________________ Class: ___________________ Date: __________
ID: Z
Exam 2
Multiple Choice
Identify the choice that best completes the statement or answers the question.
____
____
1. You wish to measure a current through a resistor. You should connect the measuring device in what way?
a. in series with the resistor
c. replace the resistor with the measuring
device
b. in parallel with the resistor
d. it depends on the circuit
2. A current of 20 A flows through a wire of length 1 m and diameter 1 mm. The potential across the wire is
1.4 V. From this table of resistivities, select the material of the wire:
Material
Copper
Silver
Gold
Tungsten
Iron
____
____
____
____
Resistivity(Ohm-m)
1.7x10-8
1.59x10-8
2.44x10-8
5.5x10-8
10.0x10-8
a. Copper
d. Tungsten
b. Silver
e. Iron
c. Gold
3. A 3 V potential difference is maintained across a 10 Ω resistor for 2 minutes. How many electrons pass
through the material?
d. 0.3
a. 2.25x1020
b. 60
e. 36
c. 3.75x1018
4. Nonohmic materials
a. all of the above
c. do not obey Ohm’s Law
b. do not include most resistors
d. include diodes
5. A one-hundred watt lightbulb and a 50-watt lightbulb are in parallel with a power supply of 100 V. What
current flows through the 100 W light bulb?
a. 1/2 A
c. None of the above
b. 2 A
d. 1 A
6. A 50Ω and a 100Ω resistor are in series with a power supply of 150 V. What amount of energy is dissipated
across the 50 Ω resistor in 3 seconds?
a. 300 J
c. 450 J
b. 100 J
d. 150 J
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Name: ________________________
____
____
____
ID: Z
7. The electric company charges a rate of $0.10 per kilowatt-hour. How much does it cost to run a 100 W bulb
for 10 hours?
a. $1
c. $0.36
b. $10
d. $0.10
8. On a circuit breaker, you have a 1200 W heater, a 60 W light bulb, and a 240 W radio. When you add a 180
W blender, the circuit breaker turns off. Assume all the devices operate at 120 V. Which of these is the
maximum allowed current for the breaker?
a. 20 A
c. 10 A
b. 13 A
d. 15 A
9. Two wires, A and B, are made of the same metal and have equal length, but the resistance of wire A is 16
times the resistance of wire B. How do their diameters compare?
a.
dA=dB
d.
b.
dA=2dB
e.
dA=4dB
1
dA= dB
2
1
dA= dB
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____ 10. When you rotate the knob of a light dimmer, what is being changed in the electric circuit?
c.
a. resistance
d. just power & current
b. current
e. all of the above
c. power
____ 11. In your house, two lightbulbs operate at 120 V, but one has a power rating of 25 W while the other has a
power rating of 100 W. Which one has the greater current flowing through it?
a. 25 W bulb
c. both have same current
b. not enough information
d. 100 W bulb
____ 12. Two space heaters in your living room are operated at 120 V. Heater 1 has twice the resistance of heater 2.
Which one will give off more heat?
a.
b.
Heater 1
Heater 2
c.
d.
2
both will give same heat
not enough information
Name: ________________________
ID: Z
____ 13. A battery has an internal resistance of 1 Ω. When it provides a current of 2 A, the potential across the battery
is 10 V. What is the ideal electromotive force provided by the battery?
a. 5 V
c.
b. 12 V
d.
____ 14. What is the equivalent resistance of this circuit?
30 V
20 V
a. 5.6 Ω
c. 5.1 Ω
b. 25 Ω
d. 4.1 Ω
____ 15. Two resistors of 7 Ω and 3Ω are in series with a 10 V battery. What is the current through the 3 Ω resistor?
a.
b.
3.33 A
1A
c.
d.
3
1.4 A
0.3 A
Name: ________________________
ID: Z
____ 16. Three resistors of 2 Ω, 4Ω , and 4Ω are in parallel with a power supply of 10 V. What is the total current
through the circuit?
a. 2.5 A
c. 10 A
b. 5 A
d. 1 A
____ 17. The ammeter in this circuit reads a current of I 3=1 A. What is the current I 1?
a.
b.
1.1 A
1.25 A
c.
d.
4
1.4 A
2.9 A
Name: ________________________
ID: Z
____ 18. Which of these equations is appropriate (ie. correct) for this circuit?
a.
b.
c.
10-6I2-2I3=0
I1+I3=I2
2I3+6I1-10=0
d.
e.
5
14+6I1-10-4I2=0
14-4I2+2I3=0
Name: ________________________
ID: Z
____ 19. In this circuit, what happens to the current in each resistor as you add resistors in parallel?
a.
Current decreases
c.
It depends on the value of the added
resistance
b. Current stays the same
d. Current increases
____ 20. In this circuit, what happens to the brightness of bulb A when you close the switch?
a.
b.
not enough information
glows brighter than before
c.
d.
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glows just the same as before
glows less than before
Name: ________________________
ID: Z
____ 21. In this figure, light bulbs A, B, and C each have a resistance of 1 Ω . How do the brightness of bulbs A and C
compare?
a.
b.
c.
bulb A is four times as bright as C
bulb A is twice as bright as C
bulb A is 1/2 as bright as C
d.
e.
bulb A is the same brightness as C
bulb A is 1/4 as bright as C
____ 22. When 2 or more resistors are connected in parallel to a battery,
a.
all of the above
b. the voltage across each resistor is the
c.
the equivalent resistance of the
combination is less than or equal to
the resistance of any one of the
resistors
d.
the total current flowing from the
battery equals the sum of the currents
flowing through each resistor
same
____ 23. Three identical resistors are connected in series to an ideal battery with V=12 V. What is the
potential across each resistor?
a.
b.
4V
2V
c.
d.
7
3V
6V
Name: ________________________
ID: Z
____ 24. In this RC circuit, the time constant is 1 µs and the resistance is 10 Ω. What is the capacitance, C?
a.
b.
c.
2 µF
0.1 µC
10 µF
d.
e.
1 µF
0.1 µF
____ 25. What happens to the voltage across the resistor R 1 when the switch is closed? The voltage will:
a.
b.
decrease
increase
c.
d.
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stay the same
not enough information given
Name: ________________________
ID: Z
____ 26. What happens to the current through the resistor R 1 when the switch S is closed?
R1
S
R3
V
R4
R2
a. decreases
c. stays the same
b. increases
____ 27. Assume each of these resistances are identical. Which resistor(s) has the least amount of current flowing
through it?
V
a.
b.
c.
R5
R2
R5
both R3 and R4 equally
both R1 and R2 equally
R4
R3
R1
d.
e.
R1
all the same
____ 28. What purpose does the third prong on a three-prong outlet serve?
a. Allow for more stability in the outlet
c. Act as a ground thus providing a
safety feature
b.
An alternative to the European system d.
of electrical outlets
No purpose
____ 29. GFCI stands for
a. Gauge for Circuit Integrity
c. Good For Cashing In
b. Ground Force Circuit Interpreter
d. Ground Fault Circuit Interrupt
____ 30. A household circuit has all of the electrical devices connected in _____________.
a. it depends on the house
c. series
b. parallel
d. a combination of series and parallel
____ 31. The correct answer to this question is “A.” Please write “A” above your name on the scantron.
a. A
c. C
b. B
d. D
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ID: Z
Exam 2
Answer Section
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