SP212 Exam 2
Name:
1) Do not open this exam until instructed to do so.
2) This exam consists of 15 multiple choice questions. Clearly circle your answers. For some questions,
relevant information might be given in the included figure.
3) You have 50 minutes to complete this exam.
4) Do not interact with anyone except Dr. Rittenhouse during the exam.
5) Do not discuss this exam with any other students who have not taken the exam.
6) When you have completed the entire exam, write your final answers on the answer sheet provided. Be
sure to write your name at the top of the answer sheet and hand it in. These will be the answers you are
graded on. Take the rest of the exam packet with you for use in exam corrections.
1. What is the magnitude of the electrostatic force acting on the −3.0 nC charge in the figure below?
A) 5.6 × 10−9 N
B) 8.3 × 10−9 N
C) 9.9 × 10−9 N
D) 2.0 × 10−9 N
E) 2.4 × 10−9 N
2. What is the x-component of the electric field at the point P in the figure below?
A) 2 × 103 N/C
B) 2.6 × 103 N/C
C) 5.0 × 103 N/C
D) 5.6 × 103 N/C
E) 7.2 × 103 N/C
~ = 4000î N/C. The
3. A dipole with dipole moment P~ = (5ĵ + 2î) × 10−30 Cm is placed in an electric field E
magnitude of the torque acting on the dipole is closest to:
A) 1 × 10−26 Nm
B) 2 × 10−26 Nm
C) 3 × 10−26 Nm
D) 4 × 10−26 Nm
E) 5 × 10−26 Nm
4. A square of side length 5 cm sits flat in the yz-plane. What is the magnitude of the flux of an electric field
~ = (2.0î − 4.0ĵ + 1.0k̂) N/C through this square?
E
A) 1.5 × 10−3 N m2 /C
B) 2.5 × 10−3 N m2 /C
C) 3 × 10−3 N m2 /C
D) 4 × 10−3 N m2 /C
E) 5 × 10−3 N m2 /C
For questions 5 and 6 two charges are placed on the x-axis. The first has size +Q and is at x = +d and the
second is of size −Q placed at the point x = −d.
5. What is the x-component of the electric field at the origin?
A) Ex = 0
B) Ex = −kQ
d2
C) Ex = kQ
d2
D) Ex = −2kQ
d2
E) Ex = 2kQ
d2
6. What is the electric potential at the origin is we set V = 0 at inifinity?
A) V
B) V
C) V
D) V
E) V
=0
= −kQ
d
= kQ
d
= −2kQ
d
= 2kQ
d
7. An insulating sphere of radius R has a charge Q uniformly distributed throughout its volume. What is
the magnitude of the electric field a distance R/2 from the center of the sphere?
A) 0
Q
B) k 2R
2
C) k RQ2
D) 2k RQ2
E) 4k RQ2
8. Two concentric spherical shells with radii 25 cm and 75 cm are oppositely charged as shown in the figure
below. If Q = 20 nC, what is the magnitude of the electric field at r = 50 cm
A) 550 N/C
B) 590 N/C
C) 720 N/C
D) 790 N/C
E) 910 N/C
9. The figure below shows a rectangular array of charged particles fixed in place, with a = 50 cm. The
charges shown are integer multiples of q1 = 3 pC and q2 = 6 pC. With V= 0 at infinity, what is the net
electric potential at the rectangle’s center?
A) 8.6 V
B) 17.3 V
C) 34.2 V
D) 0.33 V
E) 0 V
10. An isolated conducting sphere of radius R has an excess charge of +Q. If the electric potential is set
to be zero infinitely far from the sphere, what is the electric potential a distance R/4 from the center of the
sphere?
A) 0
B) 2k Q
R
C) 4k Q
R
D) k Q
R
Q
E) k 4R
11. A rod of length L sits on the x-axis as shown, and has a total charge −Q uniformly distributed on it.
Which of the following integrals have been properly set up to find the electric potential at the point P ?
R L dx
0 x+d
R
L dx
B) V = −k Q
L 0 x
R L dx
C) V = −k Q
L 0 x2
dx
Q RL
D)= −k L 0
(x + d)2
R L dx
E) V = k Q
L −d x + d
A) V = −k Q
L
~ = (1.7 + 2.2x)î where x is in meters and E is in N/C and the electric
12. In an electric field given by E
potential at x = 0 is 1.5 V, what is the electric potential at x = 2.0m?
A) −9.3 V
B) −7.8 V
C) −6.3 V
D) +7.8 V
E) +9.3 V
13. What is the total charge stored in the capacitor system shown below?
A) 2.5 µC
B) 5.0 µC
D) 6.0 µC
E) 7.0 µC
14. A parallel plate capacitor is made of two square plates of side length 2.0 cm separated by a distance of 2.5
mm. A dielectric material with dielectric constant κ fills the space between the plates. When the capacitor
is fully charged by a 12.0 V battery, it stores 3.57 × 10−10 J of energy. What is the value of the dielectric
constant κ?
A) 1.4
B) 2.1
C) 3.5
D) 7.0
E) 22.4
15. A cylindrical wire of radius 2 mm carries a uniform current density of J = 198000
of the current in the wire is closest to:
A) 1 A
B) 1.5 A
C) 2 A
D) 2.5 A
E) 3 A
C
.
m2 s
The magnitude
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