Exam 2
1
NAME:
GENERAL PHYSICS 2
(PHYS 2124)
EXAM 3
1. Four 20-Ω resistors are connected in series and the combination is connected to a 20-V
emf device. The current in any one of the resistors is:
A. 0.25A
B. 1.0A
C. 4.0A
D. 5.0A
E. 100A
2. Nine identical wires, each of diameter d and length L, are connected in series. The
combination has the same resistance as a single similar wire of length L but whose
diameter is:
A. 3d
B. 9d
C. d/3
D. d/9
E. d/81
3. Each of the resistors in the diagram has a resistance of 12 Ω. The resistance of the
entire circuit is:
A. 5.76 Ω
B. 25 Ω
C. 48 Ω
D. 120 Ω
E. none of these
Exam 2
2
4. Resistor 1 has twice the resistance of resistor 2. The two are connected in parallel and a
potential difference is maintained across the combination. The rate of thermal energy
generation in 1 is:
A. the same as that in 2
B. twice that in 2
C. half that in 2
D. four times that in 2
E. one-fourth that in 2
5. A portion of a circuit is shown, with the values of the currents given for some
branches. What is the direction and value of the current i?
A. ↓, 6A
B. ↑, 6A
C. ↓, 4A
D. ↑, 4A
E. ↓, 2A
6. For the circuit shown below, what is the upper loop equation?
A. 6  I 2  I 3  2 I 1
10 V
8
B. 6  I 2  2I 3  I1
C. 24  4I 2  4I 3  8I1
I1
D. 8I1  10  4I 3  4I 2  14  0
E. none of these
4
14 V
I2
4
I3
3
6
3
28 V
Exam 2
3
7. Suppose the current charging a capacitor is kept constant. Which graph below correctly
gives the potential difference V across the capacitor as a function of time?
8. A certain capacitor, in series with a resistor, is being charged. At the end of 10 ms its
charge is half the final value. The time constant for the process is about:
A. 0.43 ms
B. 2.3ms
C. 6.9ms
D. 10 ms
E. 14 ms
9. An electron moves in the negative x direction, through a uniform magnetic field in the
negative y direction. The magnetic force on the electron is:
A. in the negative x direction
B. in the positive y direction
C. in the negative y direction
D. in the positive z direction
E. in the negative z direction
Exam 2
4
10. The figure shows a uniform magnetic field B directed to the left and a wire carrying a
current into the page. The magnetic force acting on the wire is:
A. toward the top of the page
B. toward the bottom of the page
C. toward the left
D. toward the right
E. zero
Question 11 – 15 refer to the diagram below.
11. The neutron (N) shown in the
diagram below travels (with a V = 2
m/s) across the magnetic field lines, will
it experience a magnetic force?
A. YES
B. NO
12. The electron (e-) shown in the
diagram below travels (with a V = 1.5
m/s) along the magnetic field
lines, will it experience a magnetic
force?
A. YES
B. NO
III
I
V
N
V
I
I
p+
V
eI
e+
V
13. The proton (p+) shown in the
diagram below travels (with a V = 1.5
m/s) along the magnetic field lines, will
it experience a magnetic force?
A YES
B. NO
14. Will the stationary positron ( e+) (NOTE: a positron is just an electron with a positive
(+) charge) shown in the diagram experience a magnetic force?
A. YES
B. NO
Exam 2
5
15. From the following diagram place in order from greatest field strength to weakest
field strength the points shown.
A. I, II, III, IV
B. IV, III, II, I
C. III, II, IV, I
D. I, IV, II, III
E. II, I, IV, III
16. Which of the following will produce a magnetic field?
I.
A current-carrying wire
II.
Moving a wire through a field free region
III.
Electrons orbiting a nucleus
A. I only
B. II only
C. I and III only
D. II and III only
E. I, II, and III
17. When electric current in two parallel wires is flowing in the directions shown below,
the wires tend to:
I1
I2
A. repel each other
B. attract each other
C. exert no force
D. spin
E. none of these
Exam 2
6
18. Two long current-carrying wires are depicted in the illustration below. What is the Bfield at point P, 3 m away from the crossing point?
A. 42.4 nT, pointing into the paper
I = 2A
B. 424 nT, pointing out the paper
C. 42.4 nT, pointing out the paper
P
3m
45o
60o
D. 424 nT, pointing into the paper
E. none of these
I = 3A
19. Which graph correctly gives the magnitude of the magnetic field outside an infinitely
long straight current-carrying wire as a function of the distance r from the wire?
20. Two parallel wires carrying equal currents of 10A attract each other with a force of 1
mN. If both currents are doubled, the force of attraction will be:
A. 1mN
B. 4mN
C. 0.5mN
D. 0.25mN
E. 2mN
Exam 2
7
SHOW ALL WORK (5 points)
An electron that has velocity:

 




v  2.0  10 6 m / s i  3.0  10 6 m / s j



moves through the uniform magnetic field B  0.030T i  0.15 T  j .
(a) Find the force on the electron. (b) Repeat your calculation for a proton having the
same velocity.