### Summer 2000 Physics 102 Hour Exam 1(17 questions)

The grading button and a description of the scoring criteria are at the bottom of this page. Basic questions are marked by a single star *. More difficult questions are marked by two stars **. The most challenging questions are marked by three stars ***.

This exam consists of 17 questions; true-false questions are worth 2 points each, three-choice multiple choice questions are worth 3 points each, five-choice multiple choice questions are worth 6 points each. The maximum possible score is 77. When the exam was given, the minimum "A" score was 69; the minimum "B" was 57; the minimum "C" was 44; the minimum "D" was 31. The mean was 56.3; the median was 57. Click here to see the formula sheet that came with the exam.

### QUESTION 1**

An uncharged conductor is placed near a negative charge -q as shown to the right. What is the electric force on the uncharged conductor?

(a)   toward the charge -q
(b)   away from the charge -q
(c)   zero

### QUESTION 2*

A positive charge +Q is held along the midline equidistant from two charges +q and -q. If the positive charge +Q is released, in what direction does it move in the plane of the sheet? (Consider only electric forces.)

(a)   vertically upward
(b)   vertically downward
(c)   horizontal, to the right
(d)   horizontal, to the left
(e)   it does not move

### QUESTION 3**

A uniform electric field is directed to the right as shown in the figure. Compare Wef the work required to move a positive charge from point e to point f, with Weg, the work required to move the same charge from point e to point g.

(a)   Wef < Weg
(b)   Wef = Weg
(c)   Wef > Weg

### QUESTION 4*

Four charges all of the same magnitude, are located at the corners of a square. One is positive and three are negative as shown in the figure. What is the direction of the electric field at the center of the square, (marked with a dot in the figure)?

(a)   toward A
(b)   toward B
(c)   toward C
(d)   toward D
(e)   E = 0

### QUESTION 5**

Two capacitors, one of capacitance C and the other of capacitance 2C are connected to a battery as shown below. Compare Q1 the charge on the positive plate of capacitor C with Q2 the charge on the positive plate of capacitor 2C.

(a)   Q1 < Q2
(b)   Q1 = Q2
(c)   Q1 > Q2

### QUESTION 6*

A parallel plate capacitor is charged by connecting it to a battery. The battery is then removed, leaving the charge on the capacitor plates. What happens to the energy stored in the capacitor when the plates are pulled a small distance further apart?

(a)   It decreases.
(b)   It stays the same.
(c)   It increases.

### QUESTION 7*

The light bulbs and batteries in the two circuits are identical. Compare B1 the total brightness produced by circuit 1, with B2 the total brightness produced by circuit 2.

(a)   B1< B2
(b)   B1= B2
(c)   B1> B2

### QUESTION 8*

This and the next two questions are about the following situation:

The three charges indicated in the figure are fixed at the locations shown.

Calculate the electric potential at the origin assuming the potential is defined to be zero at infinity?

(a)   V = -18000 V
(b)   V = -13500 V
(c)   V = 0
(d)   V = +22500 V
(e)   V = +54000 V

### QUESTION 9**

Assume that the –6 µC and the +8 µC charges are already located at the positions shown. How much work is required to bring the -2 µC charge from infinitely far away to the location (-2,0) as shown in the figure?

(a)   W = + 22.5 × 10-3 J
(b)   W = + 9.0 × 10-3 J
(c)   W = 0
(d)   W = - 9.0 × 10-3 J
(e)   W = - 45.0 × 10-3 J

### QUESTION 10**

Suppose the -2 µC and the +8 µC charges are held fixed at the locations shown, but the -6 µC is released from the position (2,0). Which way would it go?

(a)   to the left
(b)   to the right
(c)   it would remain at rest

### QUESTION 11*

This and the next question are about the following situation:

In which direction is the force on charge q3 due to charges q1 and q2 pointing?

(a)   to the left
(b)   to the right
(c)   up

### QUESTION 12**

What is the magnitude of this force?

(a)   F = 1.03 × 10-3 N
(b)   F = 2.31 × 10-3 N
(c)   F = 4.56 × 10-3 N
(d)   F = 11.3 × 10-3 N
(e)   F = 18.6 × 10-3 N

### QUESTION 13**

This and the next two questions are about the following situation:

A 10 volt battery is connected to a parallel plate capacitor. The points marked a and b are specific locations on the conducting wire of the circuit. The dotted surface marked c is located exactly halfway between the plates of the capacitor.

What is the direction of the electric field between the plates of the capacitor?

(a)   upward
(b)   downward

### QUESTION 14***

What is the potential difference, Vb – Va, between point b and point a on the circuit?

(a)   -10 V
(b)   -5 V
(c)   0 V
(d)   +5 V
(e)   +10 V

### QUESTION 15**

What is the potential difference, Vc – Vb, between surface c and point b on the circuit?

(a)   -10 V
(b)   -5 V
(c)   0 V
(d)   +5 V
(e)   +10V

### QUESTION 16*

This and the next question are about the following situation:

Three capacitors are connected to a battery as shown in the diagram. The potential difference provided by the battery is 24 volts, while C1 = 8 µF, C2 = 6 µF, and C3 = 4 µF.

What is Q1, the charge on the capacitor C1?

(a)   Q1 = 6.0 × 10-5 C
(b)   Q1 = 8.4 × 10-5 C
(c)   Q1 = 10.8 × 10-5 C
(d)   Q1 = 14.4 × 10-5 C
(e)   Q1 = 19.2 × 10-5 C

### QUESTION 17*

What is Utotal, the total energy stored in all of the capacitors?

(a)   Utotal = 7.05 × 10-3 J
(b)   Utotal = 3.00 × 10-3 J
(c)   Utotal = 8.57 × 10-4 J
(d)   Utotal = 2.13 × 10-4 J
(e)   Utotal = 1.05 × 10-4 J

Scoring of True-False (T,F) Questions:
• If you mark the correct answer, you get 2 points.
• If you mark the wrong answer or if you mark neither answer, you get 0 points.
Scoring of Multiple Choice I (a,b,c) Questions:
• If you mark the correct answer, you get 3 points.
• If you mark a wrong answer or if you mark none of the answers, you get 0 points.
Scoring of Multiple Choice II (a,b,c,d,e) Questions:
• If you mark one answer and it is the correct answer, you get 6 points.
• If you mark two answers and one of them is the correct answer, you get 3 points.
• If you mark three answers and one of them is the correct answer, you get 2 points.
• If you do not mark the correct answer, or if you mark more than three answers, or if you mark none of the answers, you get 0 points.