Q. If the distance between two charges is doubled, how does the force between them change?
A.It doubles
B.It halves
C.It quadruples
D.It reduces to one-fourth
Solution
According to Coulomb's law, force is inversely proportional to the square of the distance. If the distance is doubled, the force reduces to one-fourth.
Q. If the distance between two charges is halved, how does the force between them change?
A.It doubles
B.It quadruples
C.It remains the same
D.It halves
Solution
According to Coulomb's law, the force F between two charges is inversely proportional to the square of the distance. If the distance is halved, the force becomes four times greater.
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.
