75
ELECTROSTATICS - Multiple Choice
14.
1. Which one of the following represents correct units for electric field strength?
A.
B.
C.
D.
[9401-14]
T
N /C
J/C
N • m 2 / C2
15.
2. The flow of charge per unit time defines
[9401-15]
A. power.
B. current.
C. voltage.
16. D.
The diagram
below shows two positive charges of magnitude Q and 2Q.
resistance.
16.
3. The diagram below shows two positive charges of magnitude Q and 2Q.
P
[9401-16]
P
Q
2Q
Q
2Q
Which vector best represents the direction of the electric field at point P, which is equidistant
from both charges?
Which vector best represents the direction of the electric field at point P, which is equidistant
from both charges?
B.
A.
A.
B.
C.
D.
C.
D.
–6
17. A 6.0 x 10 C charge is located 4.0 m from a –3.0 x 10 –6 C charge.
4.
2.0 m
Q1 = 6.0 x 10–6 C
2.0 m
P
Q2 = –3.0 x 10–6 C
What is the electric potential at P, halfway between the charges?
A. –4.1 x 10–2 V
B. 6.8 x 103 V
C. 1.4 x 104 V
D. 4.1 x 104 V
[9401-17]
76
ELECTROSTATICS - Multiple Choice
16. A negative charge in an electric field experiences a force accelerating it due south. What is the
5.
direction of the electric field?
[9501-16]
A.
B.
C.
D.
east
west
north
south
−6
17.
6. A − 2.3 × 10 C charge exerts a repulsive force of magnitude 0.35 N on an unknown charge
0.20 m away. What are the magnitude and polarity of the unknown charge?
[9501-17]
MAGNITUDE
POLARITY
A.
6.8 × 10 −7 C
Negative
B.
6.8 × 10 −7 C
Positive
C.
1.2 × 10 −6 C
Negative
D.
1.2 × 10 −6 C
Positive
−6
−6
18.
7. Two point charges, 2. 5 × 10 C and −5. 0 × 10 C , are placed 3.0 m apart as shown below.
P
2.5 × 10 −6 C
+
1.5 m
−5.0 × 10 C
−6
1.5 m
[9501-18]
–
What is the magnitude of the electric field at point P, midway between the two charges?
A. 0 N / C
B. 1. 0 × 10 4 N / C
C. 2. 0 × 10 4 N / C
D. 3. 0 × 10 4 N / C
−9
3.0 m from a stationary6.0 × 10 −8 C charge. How much
19.
8. A 4.0 × 10 C charge is initially located
work is required to move the 4.0 × 10 −9 C charge to a point 0.50 m from the stationary charge?
−9
4.0 × 10 C +
[9501-19]
3.0 m
+ 6. 0 × 10 −8 C
0.50 m
A.
B.
C.
D.
6.0 × 10 −7
8.6 × 10 −7
3.6 × 10 −6
4.3 × 10 −6
J
J
J
J
77
ELECTROSTATICS - Multiple Choice
−2
20.
9. Two parallel plates 4.0 × 10 m apart have a potential difference of 1 000 V. An electron is
released from the negative plate at the same instant that a proton is released from the positive plate.
Which of the following best compares their speed and kinetic energy as they strike the opposite
plate?
[9501-20]
A.
SPEED OF
ELECTRON AND PROTON
KINETIC ENERGY OF
ELECTRON AND PROTON
same
different
different
different
same
B.
C.
different
D.
same
same
15.
10. Two positive charges, equal in magnitude, are separated as shown below.
1
⊕
2
3
⊕
[9508-15]
4
In which location would the electric field strength be zero?
A.
B.
C.
D.
1
2
3
4
16.
11. An electron is positioned in an electric field. The force on the electron due to the electric field is
equal to the force of gravity on the electron. What is the magnitude of this electric field?
A. 8. 93 × 10 −30 N/ C
B. 5. 69 × 10 −12 N/ C
C. 5. 58 × 10 −11 N/ C
D. 1. 44 × 10 −9 N/ C
[9508-16]
78
ELECTROSTATICS - Multiple Choice
17. Two parallel plates 6.0 × 10 −2 m long are separated by 2.5 × 10 −2 m and have a potential difference
12.
of 850 V. Point P is located midway between the two plates as shown below.
[9508-17]
OV
P
850 V
2.5 × 10 m
−2
6.0 × 10 m
−2
What is the magnitude of the electric field at point P?
A. 1. 4 × 10 4 V/ m
B. 1. 7 × 10 4 V/ m
C. 3. 4 × 10 4 V/ m
D. 6.8 × 10 4 V/ m
−5
18.
13. A particle with a charge of 2.4 × 10 C is accelerated from rest through a potential difference
of 6.2 × 10 4 V . If the final speed of this particle is 9.3 × 103 m/s, what is the mass of the particle?
[9508-18]
A. 7. 7 × 10 −10 kg
B. 5. 2 × 10 −9 kg
C. 3. 4 × 10 −8 kg
D. 1. 5 × 10 −1 kg
−6
19.
14. Two 3.0 × 10 C point charges are placed 5.0 m apart as shown below.
5.0
m
5.0
m
P
3.0 × 10−6 C
⊕
5.0 m
What is the potential at point P due to the two charges?
A. O V
B. 5. 4 × 103 V
C. 7. 6 × 103 V
D. 1.1 × 10 4 V
⊕
3.0 × 10−6 C
[9508-19]
79
ELECTROSTATICS - Multiple Choice
15. Which of the following diagrams shows the electric field in the region of two equal but opposite
15.
point charges?
A.
B.
C.
D.
[9601-15]
−11
−9
16.
16. An electron experiences an electric force of 1.8 × 10 N at a distance of 5. 0 × 10 m from the
nucleus of an ion. The electron is moved farther away, to a distance of 2. 0 × 10 −8 m from the ion.
What is the new electric force on the electron?
[9601-16]
A. 1.1 × 10 −12 N
B.
C.
D.
4. 5 × 10 −12 N
7. 2 × 10 −11 N
2. 9 × 10 −10 N
80
ELECTROSTATICS - Multiple Choice
17.
17. What is the magnitude of the electric field at point P due to the two fixed charges as shown?
[9601-17]
5.0 × 10
−6
C
+
P
3.0 m
3.0 m
+
A.
B.
C.
D.
8.0 × 10 −6 C
3. 0 × 103 N / C
9. 4 × 103 N / C
1.3 × 10 4 N / C
3. 9 × 10 4 N/ C
18.
18. An electron is travelling in an electric field as shown.
electron
[9601-18]
parallel plates
+ + + + + + + + + + +
–
v
– – – – – – – – – – – –
Describe the electrostatic force acting on the electron while in the field.
MAGNITUDE OF FORCE
DIRECTION OF FORCE
A.
Changing
Upward
B.
Changing
Downward
C.
Constant
Upward
D.
Constant
Downward
ELECTROSTATICS - Multiple Choice
81
19.
19. A proton initially at rest is accelerated between parallel plates through a potential difference
of 300 V .
[9601-19]
proton
+
+ 300 V
0.040 m
0V
What is the maximum speed attained by the proton?
A.
7. 5 × 103 m/s
B.
1. 7 × 10 5 m/s
D.
1. 2 × 10 6 m/s
C.
2. 4 × 10 5 m/s
15.
20. Which of the following is an equivalent unit for the volt?
A.
C
s
B.
J
C
C.
N
C
D. J
[9608-15]
82
ELECTROSTATICS - Multiple Choice
4
16.
21. A proton is accelerated from rest between parallel plates with a potential difference of 3. 0 × 10 V.
[9608-16]
4
0V
−3.0 × 10 V
proton
+
–2
2.5 × 10 m
What is the maximum speed of the proton?
A. 1.3 × 101 m/s
B. 3.8 × 10 5 m/s
C. 2. 4 × 10 6 m/s
D. 1. 5 × 10 7 m/s
17. What are the magnitude and direction of the electric force on the +2. 0 × 10 −6 C charge shown
below?
[9608-17]
Q1 = −6.0 × 10
–
−6
C
q = +2. 0 × 10 −6 C
Q2 = −7.0 × 10
–
+
4.0 m
4.0 m
MAGNITUDE OF FORCE
DIRECTION OF FORCE
A.
1.1 × 10 −3 N
Left
B.
1.1 × 10 −3 N
Right
C.
1. 5 × 10 −3 N
Left
D.
1. 5 × 10 −3 N
Right
−6
C
83
18.
23.
ELECTROSTATICS - Multiple Choice
What is the electric potential energy of an electron at a distance of 5.3 × 10 −11 m from the proton in
a hydrogen atom?
[9608-18]
A. − 4.3 × 10 −18 J
B. − 8. 2 × 10 −8 J
C. − 2. 7 × 101 J
D. − 5.1 × 1011 J
16.
24. Which of the following gives correct units for electric field strength?
A.
B.
C.
D.
[9701-16]
V
C
Nm
Vm
18.
25. Electric charges are arranged as shown in the diagram below.
Q2 = 2.5 × 10 −6 C
P
Q1 = 7.5 × 10 −6 C
[9701-18]
−
+
0.20 m
0.20 m
What is the electric field (magnitude and direction) at point P, midway between the charges?
A.
B.
C.
D.
MAGNITUDE OF ELECTRIC FIELD (N/C)
DIRECTION OF ELECTRIC FIELD
1.1 × 10 6
Left
1.1 × 10 6
2.3 × 10 6
2.3 × 10 6
Right
Left
Right
84
ELECTROSTATICS - Multiple Choice
19. What is the final speed of an electron accelerated from rest through a potential difference of
26.
750 V ?
[9701-19]
A. 3.8 × 10 5 m s
B. 8.1 × 10 6 m s
C. 1. 6 × 10 7 m s
D. 2. 6 × 1014 m s
15.
27. Which of the following shows the electric field between two opposite charges of unequal
magnitude?
[9708-15]
A.
B.
C.
D.
16. What is the magnitude of the electric field at point P due to the two charges shown?
28.
− 6. 0 × 10−6 C
8. 0 × 10−6 C
+
2.0 m
A. 4. 5 × 103 N C
B. 9. 0 × 103 N C
C. 1. 4 × 10 4 N C
D. 1.8 × 10 4 N C
P
−
2.0 m
[9708-16]
85
ELECTROSTATICS - Multiple Choice
5
17.
29. What is the acceleration of a proton in a uniform 2. 5 × 10 N C electric field as shown below?
[9708-17]
E
proton
MAGNITUDE OF ACCELERATION
DIRECTION OF ACCELERATION
A.
2. 4 × 1013 m s2
Right
B.
2. 4 × 1013 m s2
Left
C.
1. 5 × 1032 m s2
Right
D.
1. 5 × 1032 m s2
Left
−6
18.
30. How much work is needed to move a −2. 0 × 10 C charge from position S to position T as shown
below?
[9708-18]
−6
− 2. 0 × 10 C
8. 0 × 10−6 C
−
+
fixed
S
2.0 m
−
3.0 m
T
A. 4.3 × 10 −2 J
B. 4.8 × 10 −2 J
C. 9.1 × 10 −2 J
D. 1.1 × 10 −1 J
19.
31. An electron, initially at rest, is accelerated through a potential difference of 600 V as shown.
600 V
–
v
0V
What is the maximum kinetic energy of the electron?
A. 3. 7 × 10 −31 J
B. 9. 6 × 10 −17 J
C. 6. 0 × 10 2 J
D. 1. 4 × 10 4 J
[9708-19]
4 . 2 × 10 −2 m
86
ELECTROSTATICS - Multiple Choice
18.
32. A cathode ray tube is adjusted so as to deflect the beam as shown.
Side View
[9801-18]
Front View
If the deflecting voltage is held constant and the accelerating voltage is then decreased, which
diagram displays the new deflection?
A.
B.
C.
D.
87
ELECTROSTATICS - Multiple Choice
19.
33. What is the change in kinetic energy of an electron that moves from the negative plate to the
positive plate in the situation shown below?
[9801-19]
0.050 m
–
–
+300 V
0V
A. A gain of 4.8 × 10 −17 J
B. A loss of 4.8 × 10 −17 J
C. A gain of 9. 6 × 10 −16 J
D. A loss of 9. 6 × 10 −16 J
−6
20.
34. Two 2. 0 × 10 C charges are positioned as shown in the diagram below.
[9801-20]
0.
m
X
−6
m
0.
60
60
2 . 0 × 10
2 . 0 × 10
C
0.
40
m
0.
40
−6
C
m
Y
What work must be done to move a 1. 2 × 10 −7 C charge from location X to location Y?
A. 3. 6 × 10 −3 J
B. 1. 5 × 10 −2 J
C. 1.8 × 10 −2 J
D. 3. 9 × 10 −2 J
88
ELECTROSTATICS - Multiple Choice
19.
35. Which of the following correctly describes the polarity of the charges X and Y?
[9808-19]
Y
X
POLARITY OF X
POLARITY OF Y
A.
Positive
Negative
B.
Positive
Positive
C.
Negative
Negative
D.
Negative
Positive
20.
36. Three positive charges are fixed as shown in the diagram below.
−6
Q2 = 5. 0 × 10
Q1 = 4.0 × 10 C
−6
+
+
0.20 m
C
Q3 = 8. 0 × 10
+
0.50 m
Calculate the net electric force on Q2 due to Q1 and Q3 .
A.
B.
C.
D.
MAGNITUDE OF FORCE
DIRECTION OF FORCE
3.1 N
Left
3.1 N
5. 9 N
5. 9 N
[9808-20]
Right
Left
Right
−6
C
89
ELECTROSTATICS - Multiple Choice
21.
37. A cathode ray tube beam deflects to the location as shown in Diagram I when a certain voltage
is applied to the deflecting plates.
[9808-21]
CRT Screen
CRT Screen
1
2
3
4
Diagram I
Diagram II
The connections to the deflecting plates are then reversed and the deflecting voltage is
reduced. Which location in Diagram II best represents the new beam position?
A. Location 1
B. Location 2
C. Location 3
D. Location 4
18. The diagram shows the electric field lines near two point charges, L and R. Identify the
38.
polarity of these point charges.
[9901-18]
L
R
POLARITY OF L
POLARITY OF R
A.
Negative
Negative
B.
Negative
Positive
C.
Positive
Negative
D.
Positive
Positive
19. An electron orbits a nucleus which carries a charge of + 9. 6 × 10 −19 C . If the electron’s orbital
39. is 2. 0 × 10 −10 m , what is its electric potential energy?
radius
A.
B.
C.
−6. 9 × 10
−3. 5 × 10
43 J
−18
−8
D. 2. 2 × 1011 J
J
J
[9901-19]
90
ELECTROSTATICS - Full Solution
5. The diagram shows a small sphere of mass 1. 5 × 10 −14 kg held in equilibrium between two parallel
1.
plates by electrostatic and gravitational forces.
[9701-B05]
q = 4.8 × 10 −19 C
4.0 × 10−3 m
V
If the plates are 4. 0 × 10 −3 m apart and the sphere carries a charge of magnitude 4.8 × 10 −19 C,
what is the potential difference V between the plates?
(7 marks)
5. A −4. 2 × 10 −6 C charge is placed between two stationary charges, Q1 and Q2 , as shown below.
2.
Q1 = 2. 5 × 10−6 C
Q2 = 7. 3 × 10−6 C
− 4. 2 × 10−6 C
−
+
[9708-B05]
+
0.020 m
0.030 m
What is the magnitude and direction of the net force on the −4. 2 × 10 −6 C charge due to the two
stationary charges?
(7 marks)
5.
3. Calculate the net electric field (magnitude and direction) at point P due to the two point charges
shown in the diagram.
(7 marks)
Q1 = 5.0 × 10−6 C
P
+
0.60 m
Q2 = − 2.5 × 10 −6 C
–
0.30 m
[9801-B05]
91
ELECTROSTATICS - Full Solution
6
5.
4. An electron moving at 7. 5 × 10 m s enters an electric field between parallel plates by
passing through a small hole in one of the plates.
[9808-B05]
0. 050 m
–
7.5 × 10 6 m s
0V
+ 250 V
(7 marks)
What is the impact speed of the electron on the second plate?
5.
5. Two charges are positioned as shown in the diagram below.
[9901-B05]
Q2 = − 2.0 µC
–
Q1 = 8. 0 µC
+
4.0 m
A
2.0 m
a) Find the magnitude and direction of the electric field at A. (Note: 1. 0 µC = 1. 0 × 10 −6 C)
(4 marks)
b) A charge placed at A experiences a force of 4. 0 × 10 −3 N towards the right. What are
the magnitude and polarity of this charge?
(3 marks)