Two identical charged spheres suspended from a common point by two massless strings of lengths $l$, are initially at a distance $d$ $\left(d\ll l\right)$ apart because of their mutual repulsion. The charges begin to leak from both the spheres at a constant rate. As a result, the spheres approach each other with a velocity $v$. Then $v$ varies as a function of the distance $x$ between the spheres, as:

A circular disc of radius $4\mathrm{cm}$ with charge density $10 \mathrm{nC}/{\mathrm{m}}^2$ is placed in $Y-Z$ plane with center at $z=0$. Find electric field at a distance of $3\mathrm{cm}$ perpendicular to plane of disc.

Assertion: When the electric flux through a closed surface is zero then the net charge inside the surface must be zero.

Reason: When the net charge inside a closed surface is zero then electric field at every point of the Gaussian surface must be zero.

Assertion: If a proton and an electron are placed in the same uniform electric field they experience accelerations of different magnitudes.

Reason: Electric force on a charge is independent of its mass.

Assertion: When a charge is placed at a corner of a square, the flux passing through the square will be zero.

Reason: When electric field and area vector are perpendicular to each other at every point, then the flux passing through that surface will be zero.

Assertion: If more electric field lines leave a Gaussian surface than those which enter into it, then the net charge enclosed by that surface will be positive.

Reason: If the net flux passing through a Gaussian surface is zero, then net charge enclosed by that surface will be zero.

Assertion: Under electrostatic conditions net electric field inside a solid conductor will be zero.

Reason: Under electrostatic conditions there will be no free electrons inside a conductor.

Assertion :- An electric dipole experiences maximum force in a uniform electric field when it is placed with its axis at right angles to the field direction.

Reason :- When the axis of a dipole is perpendicular to a uniform external electric field, then torque acting on it will be zero.

Assertion: If a positive charge is released it moves from higher potential to lower potential.

Reason: Force on positive charge is along $\overrightarrow{E}$, which is from high potential to low potential.