A large number of positive charges each of magnitude $$q$$ are placed along the $$X$$-axis at the origin and at every 1 cm distance in both the directions. The electric flux through a spherical surface of radius 2.5 cm centred at the origin is

The electric field in a region of space is given as $$\mathbf{E}=\left(5 \mathrm{NC}^{-1}\right) x \hat{i}$$. Consider point $$A$$ on the $$Y$$-axis at $$y=5 \mathrm{~m}$$ and point $$B$$ on the $$X$$-axis at $$x=2 \mathrm{~m}$$. If the potentials at points $$A$$ and $$B$$ are $$V_A$$ and $$V_B$$ respectively, then $$\left(V_B-V_A\right)$$ is

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.