Q. If the distance from the center of the Earth is doubled, what happens to the gravitational field strength?
A.It doubles.
B.It halves.
C.It becomes one-fourth.
D.It becomes zero.
Solution
The gravitational field strength varies inversely with the square of the distance from the center of the Earth, so if the distance is doubled, the field strength becomes one-fourth.
Q. If the Earth were to suddenly shrink to half its radius while keeping its mass constant, what would happen to the gravitational force at its surface?
A.It would remain the same
B.It would double
C.It would become half
D.It would become four times stronger
Solution
If the radius is halved, the gravitational force increases by a factor of 4, since F = GM/R^2.
Correct Answer: D — It would become four times stronger
Q. If the Earth were to suddenly shrink to half its radius while keeping its mass constant, what would happen to the gravitational acceleration at its surface?
A.It would double
B.It would remain the same
C.It would halve
D.It would quadruple
Solution
If the radius is halved, the gravitational acceleration would increase by a factor of 4 (g ∝ 1/R²).
Q. If the Earth were to suddenly shrink to half its radius while maintaining its mass, what would happen to the gravitational force at its surface?
A.It would double
B.It would remain the same
C.It would become half
D.It would become four times stronger
Solution
The gravitational force at the surface is inversely proportional to the square of the radius. If the radius is halved, the force becomes four times stronger.
Correct Answer: D — It would become four times stronger
Q. If the electric field at a point is 200 N/C directed towards the positive x-axis, what is the potential difference between two points A and B separated by 3m along the x-axis?
A.600 V
B.400 V
C.200 V
D.0 V
Solution
V = -E * d = -200 N/C * 3m = -600 V. The potential at B is 600 V lower than at A.
Q. If the electric field at a point is zero, what can be said about the charges producing it?
A.There are no charges nearby
B.The charges are equal and opposite
C.The charges are all positive
D.The charges are all negative
Solution
The electric field is zero when the vector sum of the electric fields due to all charges is zero, which occurs when there are equal and opposite charges.
Correct Answer: B — The charges are equal and opposite
Q. If the electric field due to a charged plane sheet is E, what is the electric field due to two parallel sheets with equal and opposite charge densities?
A.0
B.E
C.2E
D.E/2
Solution
The fields due to the two sheets add up in the region between them, resulting in a total electric field of 2E.
Q. If the electric field inside a conductor in electrostatic equilibrium is zero, what can be said about the electric field just outside the conductor?
A.It is zero
B.It is uniform
C.It is perpendicular to the surface
D.It is parallel to the surface
Solution
The electric field just outside a conductor in electrostatic equilibrium is perpendicular to the surface.
Correct Answer: C — It is perpendicular to the surface
Q. If the electric potential at a point is 10 V and the electric field is uniform, what is the work done in moving a charge of 2 C from that point to a point where the potential is 0 V?
A.20 J
B.10 J
C.5 J
D.0 J
Solution
Work done W = q(V1 - V2) = 2 C (10 V - 0 V) = 20 J.
Q. If the electric potential at a point is 150 V and the electric field is directed towards the point, what can be said about the charge creating the field?
A.It is positive
B.It is negative
C.It is neutral
D.Cannot be determined
Solution
If the electric field is directed towards the point, it indicates that the charge creating the field is negative.
Q. If the electric potential at a point is 200 V and the electric field is uniform, what is the work done in moving a charge of 0.5 C to a point where the potential is 100 V?
A.50 J
B.100 J
C.200 J
D.0 J
Solution
Work done W = q * (V1 - V2) = 0.5 C * (200 V - 100 V) = 50 J.
