PHYS2002 – Practice Final Exam 1 with Accurate Solutions-Louisiana
State University
1. Bubble in your version of the exam. You have Version A.
2. A conducting sphere has a net charge of –6.4 × 10 –17 C. What is the approximate
number of excess electrons on the sphere?
A) 300
B) 400
C) 200
D) 500
E) 100
3. Four point charges, of varying magnitude and signs, are arranged at the corners of a
square as shown. Which of the arrows labeled A, B, C, and D gives the correct direction
of the net force that acts on the charge at the upper right corner?
A) A
B) B
C) C
D) D
E) The force on the charge at the upper right is zero.
–10 Q
4. In the figure, point A is a distance L away from a point charge Q. Point B is a distance
4L away from Q. What is the ratio of the electric field at B to that at A, EB/E?
A) 1/3
B) 1/9
C) 1/16
D) 1/4
E) This cannot be determined since neither the value of Q nor the length L is specified.
, 5. Two point charges (-Q and +Q) are located on a line and separated by a distance r.
What is the electrostatic potential energy of these two charges?
A) 2kQ / r2
B) 2kQ2 / r -Q + Q
C) 2kQ / r
D) kQ2 / r r
E) kQ2 / r2
6. The effective area of each plate of a parallel plate capacitor is 2.1 m 2. The capacitor is
filled with neoprene rubber (κ = 6.4). When a 6.0-V potential difference exists across the
plates of the capacitor, the capacitor stores 4.0 µC of charge. Determine the plate
separation of the capacitor.
A) 7.2 × 10–5 m
B) 1.8 × 10–4 m
C) 3.0 × 10–4 m
D) 5.3 × 10–4 m
E) 8.2 × 10–5 m
7. Which one of the following changes will necessarily increase the capacitance of a
capacitor?
A) increasing the charge on the plates
B) placing a dielectric between the plates
C) increasing the potential difference between the plates
D) decreasing the potential difference between the plates
E) decreasing the charge on the plates
8. If the voltage of the battery in the following circuit is V = 130 V, what is the voltage
drop across R1, the 80-Ω resistor?
A) 80 V
B) 160 V
C) 58 V
D) 140 V
E) 37 V 50
V
I 50
State University
1. Bubble in your version of the exam. You have Version A.
2. A conducting sphere has a net charge of –6.4 × 10 –17 C. What is the approximate
number of excess electrons on the sphere?
A) 300
B) 400
C) 200
D) 500
E) 100
3. Four point charges, of varying magnitude and signs, are arranged at the corners of a
square as shown. Which of the arrows labeled A, B, C, and D gives the correct direction
of the net force that acts on the charge at the upper right corner?
A) A
B) B
C) C
D) D
E) The force on the charge at the upper right is zero.
–10 Q
4. In the figure, point A is a distance L away from a point charge Q. Point B is a distance
4L away from Q. What is the ratio of the electric field at B to that at A, EB/E?
A) 1/3
B) 1/9
C) 1/16
D) 1/4
E) This cannot be determined since neither the value of Q nor the length L is specified.
, 5. Two point charges (-Q and +Q) are located on a line and separated by a distance r.
What is the electrostatic potential energy of these two charges?
A) 2kQ / r2
B) 2kQ2 / r -Q + Q
C) 2kQ / r
D) kQ2 / r r
E) kQ2 / r2
6. The effective area of each plate of a parallel plate capacitor is 2.1 m 2. The capacitor is
filled with neoprene rubber (κ = 6.4). When a 6.0-V potential difference exists across the
plates of the capacitor, the capacitor stores 4.0 µC of charge. Determine the plate
separation of the capacitor.
A) 7.2 × 10–5 m
B) 1.8 × 10–4 m
C) 3.0 × 10–4 m
D) 5.3 × 10–4 m
E) 8.2 × 10–5 m
7. Which one of the following changes will necessarily increase the capacitance of a
capacitor?
A) increasing the charge on the plates
B) placing a dielectric between the plates
C) increasing the potential difference between the plates
D) decreasing the potential difference between the plates
E) decreasing the charge on the plates
8. If the voltage of the battery in the following circuit is V = 130 V, what is the voltage
drop across R1, the 80-Ω resistor?
A) 80 V
B) 160 V
C) 58 V
D) 140 V
E) 37 V 50
V
I 50
