Multiple Choice Test For FPSC, PPSC, NTS, CSS
And Various Exams
Subject Physics Chapter # 21 ELECTRIC CHARGE
1. A coulomb is the same as:
A. an ampere/second
B. half an ampere·second2
C. an ampere/meter2
D. an ampere·second
E. a newton·meter2
ans: D
2. A kiloampere·hour is a unit of:
A. current
B. charge per time
C. power
D. charge
E. energy
ans: D
3. The magnitude of the charge on an electron is approximately:
A. 1023 C
B. 10-23 C
C. 1019 C
D. 10-19 C
E. 109 C
ans: D
4. The total negative charge on the electrons in 1 mol of helium (atomic number 2, molar mass
4) is:
A. 4 . 8 × 104 C
B. 9 . 6 × 104 C
C. 1 . 9 × 105 C
D. 3 . 8 × 105 C
E. 7 . 7 × 105 C
ans: C
5. The total negative charge on the electrons in 1 kg of helium (atomic number 2, molar mass 4)
is:
A. 48 C
B. 2 . 4 × 107 C
C. 4 . 8 × 107 C
D. 9 . 6 × 108 C
E. 1 . 9 × 108 C
ans: C
6. A wire carries a steady current of 2 A. The charge that passes a cross section in 2 s is:
A. 3 . 2 × 10-19 C
B. 6 . 4 × 10-19 C
C. 1 C
D. 2 C
E. 4 C
ans: E
7. A wire contains a steady current of 2 A. The number of electrons that pass a cross section in
2 s is:
A. 2
B. 4
C. 6 . 3 × 1018
D. 1 . 3 × 1019
E. 2 . 5 × 1019
ans: E
8. The charge on a glass rod that has been rubbed with silk is called positive:
A. by arbitrary convention
B. so that the proton charge will be positive
C. to conform to the conventions adopted for G and m in Newton’s law of gravitation
D. because like charges repel
E. because glass is an insulator
ans: A
9. To make an uncharged object have a negative charge we must:
A. add some atoms
B. remove some atoms
C. add some electrons
D. remove some electrons
E. write down a negative sign
ans: C
10. To make an uncharged object have a positive charge:
A. remove some neutrons
B. add some neutrons
C. add some electrons
D. remove some electrons
E. heat it to cause a change of phase
ans: D
11. When a hard rubber rod is given a negative charge by rubbing it with wool:
A. positive charges are transferred from rod to wool
B. negative charges are transferred from rod to wool
C. positive charges are transferred from wool to rod
D. negative charges are transferred from wool to rod
E. negative charges are created and stored on the rod
ans: D
12. An electrical insulator is a material:
A. containing no electrons
B. through which electrons do not ?ow easily
C. that has more electrons than protons on its surface
D. cannot be a pure chemical element
E. must be a crystal
ans: B
13. A conductor is distinguished from an insulator with the same number of atoms by the number of:
A. nearly free atoms
B. electrons
C. nearly free electrons
D. protons
E. molecules
ans: C
14. A neutral metal ball is suspended by a string. A positively charged insulating rod is placed
near the ball, which is observed to be attracted to the rod. This is because:
A. the ball becomes positively charged by induction
B. the ball becomes negatively charged by induction
C. the number of electrons in the ball is more than the number in the rod
D. the string is not a perfect insulator
E. there is a rearrangement of the electrons in the ball
ans: E
15. A positively charged insulating rod is brought close to an object that is suspended by a string.
If the object is attracted toward the rod we can conclude:
A. the object is positively charged
B. the object is negatively charged
C. the object is an insulator
D. the object is a conductor
E. none of the above
ans: E
16. A positively charged insulating rod is brought close to an object that is suspended by a string.
If the object is repelled away from the rod we can conclude:
A. the object is positively charged
B. the object is negatively charged
C. the object is an insulator
D. the object is a conductor
E. none of the above
ans: A
17. A positively charged metal sphere A is brought into contact with an uncharged metal sphere
B. As a result:
A. both spheres are positively charged
B. A is positively charged and B is neutral
C. A is positively charged and B is negatively charged
D. A is neutral and B is positively charged
E. A is neutral and B is negatively charged
ans: A
18. The leaves of a positively charged electroscope diverge more when an object is brought near
the knob of the electroscope. The object must be:
A. a conductor
B. an insulator
C. positively charged
D. negatively charged
E. uncharged
ans: C
19. A negatively charged rubber rod is brought near the knob of a positively charged electroscope.
The result is that:
A. the electroscope leaves will move farther apart
B. the rod will lose its charge
C. the electroscope leaves will tend to collapse
D. the electroscope will become discharged
E. nothing noticeable will happen
ans: C
20. An electroscope is charged by induction using a glass rod that has been made positive by
rubbing it with silk. The electroscope leaves:
A. gain electrons
B. gain protons
C. lose electrons
D. lose protons
E. gain an equal number of protons and electrons
ans: A
21. Consider the following procedural steps:
1. ground an electroscope
2. remove the ground from the electroscope
3. touch a charged rod to the electroscope
4. bring a charged rod near, but not touching, the electroscope
5. remove the charged rod
To charge an electroscope by induction, use the sequence:
A. 1, 4, 5, 2
B. 4, 1, 2, 5
C. 3, 1, 2, 5
D. 4, 1, 5, 2
E. 3, 5
ans: B
22. A small object has charge Q . Charge q is removed from it and placed on a second small object.
The two objects are placed 1 m apart. For the force that each object exerts on the other to be
a maximum. q should be:
A. 2Q
B. Q
C. Q/ 2
D. Q/ 4
E. 0
ans: C
23. Two small charged objects attract each other with a force F when separated by a distance
d . If the charge on each object is reduced to one-fourth of its original value and the distance
between them is reduced to d/ 2 the force becomes:
A. F/ 16
B. F/ 8
C. F/ 4
D. F/ 2
E. F
ans: C
24. Two identical conducting spheres A and B carry equal charge. They are separated by a distance
much larger than their diameters. A third identical conducting sphere C is uncharged. Sphere
C is first touched to A, then to B, and finally removed. As a result, the electrostatic force
between A and B, which was originally F , becomes:
A. F/ 2
B. F/ 4
C. 3F/ 8
D. F/ 16
E. 0
ans: C
25. Two particles, X and Y, are 4 m apart. X has a charge of 2Q and Y has a charge of Q . The
force of X on Y:
A. has twice the magnitude of the force of Y on X
B. has half the magnitude of the force of Y on X
C. has four times the magnitude of the force of Y on X
D. has one-fourth the magnitude of the force of Y on X
E. has the same magnitude as the force of Y on X
ans: E
26. The units of 1 / 4p 0 are:
A. N2C2
B. N · m / C
2
C. N2 · m2 / C
2
D. N · m2 / C
2
E. m2 / C
ans: D
27. A 5 . 0-C charge is 10 m from a -2 . 0-C charge. The electrostatic force on the positive charge is:
A. 9 . 0 × 108 N toward the negative charge
B. 9 . 0 × 108 N away from the negative charge
C. 9 . 0 × 109 N toward the negative charge
D. 9 . 0 × 109 N away from the negative charge
E. none of these
ans: A
28. Two identical charges, 2 . 0 m apart, exert forces of magnitude 4 . 0 N on each other. The value
of either charge is:
A. 1 . 8 × 10-9 C
B. 2 . 1 × 10-5 C
C. 4 . 2 × 10-5 C
D. 1 . 9 × 105 C
E. 3 . 8 × 105 C
ans: C
29. Two particles have charges Q and -Q (equal magnitude and opposite sign). For a net force of
zero to be exerted on a third charge it must be placed:
A. midway between Q and -Q
B. on the perpendicular bisector of the line joining Q and -Q , but not on that line itself
C. on the line joining Q and -Q , to the side of Q opposite -Q
D. on the line joining Q and -Q , to the side of -Q opposite Q
E. at none of these places (there is no place)
ans: E
30. Particles 1, with charge q1 , and 2, with charge q2 , are on the x axis, with particle 1 at x = a
and particle 2 at x = -2a . For the net force on a third charged particle, at the origin, to be
zero, q1 and q2 must be related by q2 =:
A. 2q1
B. 4q1
C. -2q1
D. -4q1
E. -q1 / 4
ans: B
31. Two particles A and B have identical charge Q . For a net force of zero to be exerted on a third
charged particle it must be placed:
A. midway between A and B
B. on the perpendicular bisector of the line joining A and B but away from the line
C. on the line joining A and B, not between the particles
D. on the line joining A and B, closer to one of them than the other
E. at none of these places (there is no place)
ans: A
32. A particle with charge 2- µC is placed at the origin, an identical particle, with the same charge,
is placed 2 m from the origin on the x axis, and a third identical particle, with the same charge,
is placed 2 m from the origin on the y axis. The magnitude of the force on the particle at the
origin is:
A. 9 . 0 × 10-3 N
B. 6 . 4 × 10-3 N
C. 1 . 3 × 10-2 N
D. 1 . 8 × 10-2 N
E. 3 . 6 × 10-2 N
ans: C
33. Charge Q is spread uniformly along the circumference of a circle of radius R . A point particle
with charge q is placed at the center of this circle. The total force exerted on the particle can
be calculated by Coulomb’s law:
A. just use R for the distance
B. just use 2R for the distance
C. just use 2pR for the distance
D. the result of the calculation is zero
E. none of the above
ans: D
34. A particle with charge Q is on the y axis a distance a from the origin and a particle with charge
q is on the x axis a distance d from the origin. The value of d for which the x component of
the force on the second particle is the greatest is:
A. 0
B. a
C. v2a
D. a/ 2
E. a/ v2
ans: E
35. In the Rutherford model of the hydrogen atom, a proton (mass M , charge Q ) is the nucleus
and an electron (mass m , charge q ) moves around the proton in a circle of radius r . Let k
denote the Coulomb force constant (1 / 4p 0 ) and G the universal gravitational constant. The
ratio of the electrostatic force to the gravitational force between electron and proton is:
A. kQq/GMmr2
B. GQq/kMm
C. kMm/GQq
D. GMm/kQq
E. kQq/GMm
ans: E
36. A particle with a charge of 5 10-6 C and a mass of 20 g moves uniformly with a speed of
× 6
7m / s in a circular orbit around a stationary particle with a charge of -5×10- C. The radius
of the orbit is:
A. 0
B. 0 . 23 m
C. 0 . 62 m
D. 1 . 6
E. 4 . 4m
ans: B
37. Charge is distributed uniformly on the surface of a spherical balloon (an insulator). A point
particle with charge q is inside. The electrical force on the particle is greatest when:
A. it is near the inside surface of the balloon
B. it is at the center of the balloon
C. it is halfway between the balloon center and the inside surface
D. it is anywhere inside (the force is same everywhere and is not zero)
E. it is anywhere inside (the force is zero everywhere)
ans: E
38. Charge is distributed on the surface of a spherical conducting shell. A point particle with
charge q is inside. If polarization e?ects are negligible the electrical force on the particle is
greatest when:
A. it is near the inside surface of the balloon
B. it is at the center of the balloon
C. it is halfway between the balloon center and the inside surface
D. it is anywhere inside (the force is same everywhere and is not zero)
E. it is anywhere inside (the force is zero everywhere)
ans: A
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