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Question (1)

QN0038910

A hollow metal sphere of radius is charged such that the potential on its surface is . The potential at a distance of from the centre of the sphere is

(A)
zero
(B)
(C)
(D)

Correct Answer: B

Explanation:

Potential at any point inside the sphere potential at the surface of the sphere .

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Question (2)

QN0038911

The potential energy of a system of two charges is negative when

(A)
both the charges are positive
(B)
both the charges are negative
(C)
one charge is positive and other is negative
(D)
both the charges are separated by infinite distance

Correct Answer: C

Explanation:

The potential energy is negative whenever there is attraction. Since a positive and negative charge attract each other therefore their energy is negative. When both the charges are separated by infinite distance, they do not attract each other and their energy is zero.

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Question (3)

QN0038912

Figure shows a system of three positive charges placed at the vertices of an equilateral triangle. To decrease the potential energy of the system,

(A)
a positive charge should be placed at centroid.
(B)
a negative charge should be placed at centroid.
(C)
distance between the charges should be decreased.
(D)
it should be rotated by an angle of radian.

Correct Answer: C

Explanation:

Potential energy decreases whenever there is attraction. A negative charge placed at centroid causes attraction.

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Question (1)

A hollow metal sphere of radius is charged such that the potential on its surface is . The potential at a distance of from the centre of the sphere is

Explanation:

Link:

Question (2)

The potential energy of a system of two charges is negative when

Explanation:

Link:

Question (3)

Figure shows a system of three positive charges placed at the vertices of an equilateral triangle. To decrease the potential energy of the system,

Explanation:

Link:

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