ame: ________________________ Class: ___________________ Date: __________
Exam 3--PHYS 202--S14
Multiple Choice
Identify the choice that best completes the statement or answers the question.
1. Which of these statements is always true?
a. resistors in parallel have the same voltage
b. the current for resistors in parallel is the same
c. the equivalent resistance of resistors in parallel
is bigger than any one of the resistors
d. the sum of the potentials for resistors in series
is zero
2. The terminal voltage of a battery is always
____________ than the electromotive force
because of _______________.
a. smaller, internal resistance
b. larger, large current
c. smaller, Ohm’s law
d. larger, ε
3. An ohm is a unit of
a. potential difference
b. inductance
c. resistance
d. resistivity
e. current
4. Consider this circuit. If one of the 2 Ω resistors is
removed, what happens to the voltage across the
remaining resistor?
6. Consider this circuit. Which of the following
graphs represents the current versus time after the
switch is closed and current is allowed to flow in
the circuit.
a. A
b. B
c. C
d. D
7. The third prong in the electrical outlet provides
protection from _______________.
a. very wet areas
b. too much current on a circuit
c. faulty devices
d. your gossipy aunt
8. Which of the following equations for this circuit is
correct?
a.
b.
c.
d.
it decreases
it is the same
it increases
it depends on how quickly you remove the
resistor
5. For the above circuit, what happens to the total
current coming off of the battery if you remove one
of the resistors?
a. it decreases
b. it increases
c. it remains the same
a.
b.
c.
d.
1
-6I2+10+4I1+14=0
-6+10+6I2=0
14-4I1+6I3=0
14-4I3+6=0
ame: ________________________
13. A capacitor is allowed to fully discharge. Which of
these graphs represents the voltage versus time for
that capacitor?
9. If the switch S is closed, what happens to the
current through R1?
a. stays the same
b. increases
c. decreases
d. not enough information
10. You turn on a light in your house. What happens
to the potential across other applicances on the
same circuit?
`
a. A
b. B
c. C
d. D
14. Consider this circuit. Which of the equations is a
correct use of the loop rule?
a. the potential increases
b. the potential decreases
c. the potential stays the same
11. Consider these wires with the currents as labeled.
What is the magnitude and direction of I?
a. V-I1R1-I2R2-I3R3=0
b. -I1R1-I4R4-V=0
c. +I3R3-I2R2=0
d. +I2R2-I1R1-V=0
15. What happens to the equivalent resistance of a
parallel circuit as you add resistors in parallel?
a. Req increases
b. Req decreases
c. Req stays the same
d. It depends on the value of the added resistance
a. 35 A to the right
b. 25 A to the right
c. 10 A to the left
d. 20 A to the left
12. Which of these statements about a household
circuit is true:
I. The household circuit is a series circuit.
II. All devices in a household circuit operate at the
same current.
III. As you add more devices to a household circuit,
the total current increases.
IV. A ground fault circuit interrupt turns off if
Iin>Iout for any particular device.
a. III
b. I & IV
c. III & IV
d. II & III
2
ame: ________________________
Problem
16. (20 pts) Calculate all of the currents in this circuit. Include the magnitude and direction.
Bonus (3 pts): Solve the system of equations by Gaussian elimination.
3
ame: ________________________
17. (20 pts) Calculate the voltage and current for each of these resistors. Also, calculate the equivalent resistance.
4
ame: ________________________
18. (8 pts) Consider an RC circuit with a capacitor of 2
µF in series with a 4 MΩ resistor and a 10 V
battery.
19. (7 pts) Now, remove the battery from the RC
circuit in the previous problem.
a) What is the current through the circuit at t=16
seconds?
1) How long does the capacitor require to fully
charge?
b) Sketch a plot of current vs. time as the capacitor
is discharging.
2) What is the charge on the capacitor after 8
seconds?
3) Sketch a plot of the charge vs time as the
capacitor is charging.
.
.
5
ame: ________________________
21. (5 points) Describe, in 25 words or less, how a
Ground Fault Circuit Interrupt operates.
20. (10 pts) What must be the maximum allowed
current in the circuit breaker to accommodate all of
these electrical devices?
.
6
ID: A
Exam 3--PHYS 202--S14
Answer Section
MULTIPLE CHOICE
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
A
A
C
B
A
A
C
B
B
C
B
C
A
C
B
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
PROBLEM
16. ANS:
.
PTS: 1
17. ANS:
.
PTS: 1
18. ANS:
.
PTS: 1
19. ANS:
,
PTS: 1
20. ANS:
.
PTS: 1
1
ID: A
21. ANS:
.
PTS: 1
2