A solid sphere of radius $$R$$ carries a positive charge $$Q$$ distributed uniformly throughout its volume. A very thin hole is drilled through it's centre. A particle of mass $$m$$ and charge $$-$$q performs simple harmonic motion about the centre of the sphere in this hole. The frequency of oscillation is
Assertion (A) In a region of constant potential, the electric field is zero and there can be no charge inside the region.
Reason (R) According to Gauss law, charge inside the region should be zero if electric field is zero.
Statement (A) Inside a charged hollow metal sphere, $$E=0, V \neq 0$$, (where, $$E=$$ electric field, $$V=$$ electric potential).
Statement (B) The work done in moving a positive charge on an equipotential surface is zero.
Statement (C) When two like charges are brought closer, their mutual electrostatic potential energy will increase.
The electrons take $$40 \times 10^3$$ s to dirift from one end of a metal wire of length 2 m to its other end. The area of cross-section of the wire is $$4 \mathrm{~mm}^2$$ and it is carrying a current of 1.6 A. The number density of free electrons in the metal wire is