Name: ________________________ Class: ___________________ Date: __________
Exam 3--PHYS 202--S15
Multiple Choice
Identify the choice that best completes the statement or answers the question.
1. Consider this circuit. Which of these equations is
correct?
a.
b.
c.
d.
3. Which of these plots shows the current vs time for
a charging capacitor?
I1+I2=I3
I1+4-+2I1-2=0
2-2I1+8=0
2-2I1-4+2I2=0
a.
b.
c.
d.
2. This multiloop circuit has 6 distinct currents.
Which of these equations is correct?
A
B
C
D
4. Which of these statements is always true?
a. the current for resistors in parallel is the same
b. resistors in parallel have the same voltage
c. the sum of the potentials for resistors in series
is zero
d. the equivalent resistance of resistors in parallel
is bigger than any one of the resistors
5. If the switch S is closed, what happens to the
potential across R2?
a.
b.
c.
d.
I3+I6=I4
I1+I5=I4
I2+I6=I5
I1-I2=I3
a.
b.
c.
d.
1
increases
decreases
stays the same
not enough information
9. This figure shows a wire between the poles of a
magnet. At the location of the wire, what is the
direction of the magnetic field?
6. 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.
a.
b.
c.
d.
e.
IV. A ground fault circuit interrupt turns off if
Iin>Iout for any particular device.
a.
b.
c.
d.
down
to the left
to the right
out of the page
up
10. Consider the figure in the previous question. If a
current in the wire is travelling out of the page,
what is the direction of the force on the wire?
a. to the right
b. out of the page
c. down
d. to the left
e. up
I & IV
III & IV
III
II & III
7. What does GFCI do?
a. protects you from magnetic fields
b. provides a clear path to ground
c. turns off the circuit if the current exceeds a
certain amount
d. checks if Iin>Iout
11. The point A is equidistance between these two,
long parallel wires. What is the direction of the
magnetic field at point A due to the two wires?
8. This is a true statement: “a monopole does not
exist.” Which of these is the best reason for why
this is true?
a. ferromagnetic materials are able to be
magnetized
b. a current in a wire can generate a magnetic
field
c. permanent magnets are magnetic because their
magnetic domains all line up
d. moving electrons cause magnetic fields
a.
b.
c.
d.
e.
2
To the left
To the right
Into the page
Out of the page
There is no magnetic field at A
13. This loop of wire, which sits in a B-field directed
to the right, has a current in the direction shown by
the arrows. The loop is allowed to rotate about an
axis shown by the dotted line. What is the direction
the loop will turn?
12. A positive particle approaches a current-carrying
wire as shown here. What direction will the
particle go?
a.
b.
c.
d.
e.
left
right
out of the page
into the page
it will go back the way it came (up)
a.
b.
counterclockwise
clockwise
14. Which of these statements about the magnetic force
on a charged particle travelling through a magnetic
field is true:
I. The magnetic force is a centripetal force.
II. The magnetic force is always perpendicular to
the velocity.
III. The magnetic force always causes circular
motion.
a. I & III
b. II & III
c. I & II
d. II only
e. all of these are true
3
Problem
15. (20 pts) Calculate the three currents in this circuit. Extra credit (5pts): complete the calculation by Gaussian
elimination (aka row reduction).
4
16. (15 pts) Consider this circuit.
a) What is the voltage across R 3, the 1-ohm resistor? V3=________
b) What is the total current in the circuit? I=_____________
c) What is the current through R 2, the 6-ohm resistor? I2=________
17. (10 pts) In 2-4 sentences, describe how one of the household safety devices we discussed in class (third prong,
GFCI, or circuit breaker) functions. In your description, include the scenario in which the device would be useful
and what happens when the device is utilized.
5
18. (10 pts) Consider a series RC circuit for which R =
1.0 MΩ, C=5.0 µF, and ε=30.0 V. Initially the
capacitor has no charge.
19. (10 pts) A particle carrying a -10 C
charge moves with velocity v = 3j -4k m/s
through a uniform magnetic field B = 1i + 2j
T. What is the force, in vector notation, on
the charged particle?
a) When connected to the battery and resistor, what
is the charge on the capacitor after 10.0 seconds?
b) How long does is required for the capacitor to
become fully charged?
c) Sketch a plot of how the charge on the capacitor
varies with time as it is charging.
.
6
20. (10 pts) A positive particle moves into the B-field of a mass spectrometer; the particle is moving at a speed of 4
m/s. The magnetic field has a magnitude of 16.0 T, and the radius of the particle’s path is 0.5 m. Following is a
table with the masses and charges of some imaginary particles. Which is this particular particle?
If the positive particle is traveling through a B-field as shown (in the -z direction), sketch the path it will take.
7
ID: A
Exam 3--PHYS 202--S15
Answer Section
MULTIPLE CHOICE
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
D
C
A
B
B
B
D
D
C
E
E
A
A
E
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
REF: S15
REF: S15
REF: S15
REF: S15
REF: S15
REF: S15
REF: S15
PROBLEM
15. ANS:
.
PTS: 1
16. ANS:
.
PTS: 1
17. ANS:
.
PTS: 1
18. ANS:
.a) 130 microCoulombs
b) 50 s
PTS: 1
19. ANS:
.
PTS: 1
1
ID: A
20. ANS:
Mamnium
PTS: 1
2