Three equal charges, each +q, are placed on the corners of an equilateral triangle. The electric field intensity at the centroid of the triangle is

Q.Three equal charges, each +q, are placed on the corners of an equilateral triangle. The electric field intensity at the centroid of the triangle is
(a) kq/r2
(b) 3kq/r2
(c) √3 kq/r2
(d) zero
Ans: D

Two particles of masses in the ratio 1 : 2, with charges in the ratio 1 : 1, are placed at rest in a uniform electric field. They are released and allowed to move for the same time. The ratio of their kinetic energies will be finally

Q.Two particles of masses in the ratio 1 : 2, with charges in the ratio 1 : 1, are placed at rest in a uniform electric field. They are released and allowed to move for the same time. The ratio of their kinetic energies will be finally
(a) 2 : 1
(b) 8 : 1
(c) 4 : 1
(d) 1 : 4
Ans: A

An isolated charge q1 of mass m is suspended freely by a thread of length l. Another charge q2 is brought near it (r >> l). When q1 is in equilibrium, tension in thread will be

Q. An isolated charge q1 of mass m is suspended freely by a thread of length l. Another charge q2 is brought near it (r >> l). When q1 is in equilibrium, tension in thread will be
Electrostatics

(a) mg
(b) > mg
(c) < mg
(d) none of these
Ans: B

Two point charges repel each other with a force of 100N. One of the charges is increased by 10%, and the other is reduced by 10%. The new force of repulsion at the same distance would be

Q: Two point charges repel each other with a force of 100N. One of the charges is increased by 10%, and the other is reduced by 10%. The new force of repulsion at the same distance would be
(a) 100 N
(b) 121 N
(c) 99 N
(d) none of these
Ans: C

Two particles A and B (B is right of A) having charges 8×10-6C and 2×10-6C, respectively, are held fixed with separation of 20cm. Where should a third charged particle be placed so that it does not experience a net electric force

Q.Two particles A and B (B is right of A) having charges 8×10-6C and 2 × 10-6C respectively, are held fixed with separation of 20cm. Where should a third charged particle be placed so that it does not experience a net electric force
(a) 5 cm right of B
(b) 5 cm left of A
(c) 20 cm left of A
(d) 20 cm right of B

Ans: D