Name: ________________________
Exam 3--PHYS 202--S16
Multiple Choice
Identify the choice that best completes the statement or answers the question.
1. Which of these resistors has the smallest current?
4. Current has these basic SI units:
a. volts/meter
b. tesla*meter
c. coulombs/second
d. newtons/second
e. volts/farad
5. Which of these rules for resistors in parallel is
correct?
a.
b.
c.
d.
e.
I. Resistors in parallel must have the same current.
II. Resistors in parallel must have the same voltage.
III. For resistors in parallel, the total voltage across
the resistors is equal to the sum of the voltage
across the individual resistors.
IV. For resistors in parallel, the equivalent
resistance is always less than the smallest resistor.
R1
R2
R3
R5
not enough information
2. Which has a bigger resistance, a hair dryer (1000
W) or a light bulb (100 W)?
a.
b.
c.
d.
a.
b.
c.
d.
e.
light bulb
hair dryer
both the same
not enough info to tell
6. Which of these statements about a household
circuit is true:
I. The household circuit is a parallel circuit.
II. All devices in a household circuit operate at the
same voltage.
III. As you add more devices to a household circuit,
the total current increases.
IV. A circuit breaker turns off if the total current
exceeds some predetermined value.
a. II & III
b. III & IV
c. all of these are correct
d. I & II
e. I, II, & III
3. What is the current in the 6Ω resistor (R 2)?
a.
b.
c.
d.
e.
II & III
I & III
II & IV
I & IV
II only
3A
54 A
18 A
108 A
6A
1
7. Consider this circuit. Which of these equations is
correct?
10. What is the initial direction of this positively
charged particle when it enters the magnetic field
as shown?
a.
b.
c.
d.
e.
a.
b.
c.
d.
I1+I2+I3=0
3-2I1+6-6I2-5=0
5+6I2-6=0
3+2I1+5+6I2=0
8. Which of these plots shows the
for a charging capacitor?
11. A positively charged particle enters a magnetic
field as shown. What is the force acting on the
particle?
charge vs time
a.
b.
c.
d.
e.
a.
b.
c.
d.
into the page
right
left
up
out of the page
into the page
out of the page
left
right
down
12. This figure shows the path of a charged particle.
What is the direction of the magnetic field that has
caused this motion?
A
B
C
D
9. Which of these statements is true?
a.
b.
c.
d.
magnetic monopoles do not exist
opposite poles of a magnet attract
all permanent magnets are ferromagnetic
all of these are true
a.
b.
c.
d.
2
into the page
out of the page
up
down
13. A proton enters an electric field as shown. What
must be the direction of a magnetic field, B, such
that the proton will go undeflected?
a.
b.
c.
d.
e.
left
into the page
out of the page
right
up
3
Problem
14. (20 pts) Calculate the three currents in this circuit. Give the magnitude and circle the correct direction. For 5 pts
extra credit, solve the equations by Gaussian elimination (ie., create an identity matrix).
4
15. (5 pts) Pick one of the safety features in the
electrical systems in your house. Write 2-3
sentences about what it protects your from and how
it operates.
16. (10 pts) A particle carrying a +2.0 C
charge moves with velocity v = 2i + 3j m/s
through a uniform magnetic field B = 3j - 2k
T. What is the force, in vector notation, on
the charged particle?
.
.
5
17. (15 pts) Find the voltage and current for each of these resistors:
.
6
19. (8 pts) A current of 20 A flows through a wire of
length 1 m and cross-sectional area 7.85x10 -7 m2.
The potential across the wire is 1.4 V. From this
table of resistivities, select the material of the wire:
18. (12 pts) Consider a series RC circuit for which R =
2.0 MΩ, C=5.0 µF, and ε=10.0 V. The capacitor
initially has no charge; then, it is connected to the
battery and resistor.
a) What is the time constant for this circuit?
Material
Copper
Silver
Gold
Tungsten
Iron
b) What is the current after 5.0 seconds?
c) How long does it take to fully charge the
capacitor?
d) What is the charge after 100 seconds?
e) Sketch a plot of charge versus time for this
charging capacitor.
.
7
Resistivity(Ohm-m)
1.7x10-8
1.59x10-8
2.44x10-8
5.5x10-8
10.0x10-8
ID: A
Exam 3--PHYS 202--S16
Answer Section
MULTIPLE CHOICE
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
C
A
A
C
C
C
C
B
D
A
B
B
C
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
REF: S15-Final
REF:
REF:
REF:
REF:
REF:
REF:
REF:
S15
S15-Final
S15-Final
S15--Final
S15--Final
S16
S16
PROBLEM
14. ANS:
.
PTS: 1
15. ANS:
.
PTS: 1
16. ANS:
.
PTS: 1
17. ANS:
.
PTS: 1
18. ANS:
.
PTS: 1
19. ANS:
tungsten
PTS: 1
1