Electrostatics Question 264

Question: A dielectric slab of thickness d is inserted in a parallel plate capacitor whose negative plate is at x=0 and positive plate is at x=3d . The slab is equidistant from the plates. The capacitor is given some charge. As one goes from 0 to 3d [IIT-JEE 1998]

Options:

A) r

B) 2r

C) r/2

D) r/4

Show Answer

Answer:

Correct Answer: D

Solution:

Charge q will momentarily come to rest at a distance r from charge Q when all it’s kinetic energy converted to potential energy i.e. 12mv2=14πε0.qQr

Therefore the distance of closest approach is given by r=qQ4πε0.2mv2

therefore r1v2

Hence if v is doubled, r becomes one fourth.



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