For a uniformly charged ring of radius $R$,the electric field on its axis has the largest magnitude at a distance $h$ from its centre. Then the value of $h$ is

$A$ ring of radius $R$ has charge $-Q$ distributed uniformly over it. The charge that should be placed at the center of the ring such that the electric field becomes zero at a point on the axis of the ring at a distance $R$ from the center of the ring will be:

The linear charge densities of two infinitely long thin and parallel wires are $4 \ Cm^{-1}$ and $8 \ Cm^{-1}$,and the separation between them is $4 \ cm$. The electric field intensity at the midpoint on the line joining them is:

$A$ conducting sphere of radius $10 \, cm$ has an unknown charge. If the electric field at a distance $20 \, cm$ from the centre of the sphere is $1.2 \times 10^3 \, N \, C^{-1}$ and points radially inwards,the net charge on the sphere is:

Two charges,each equal to $\eta q$ (where $\eta^{-1} < \sqrt{3}$),are placed at two corners of an equilateral triangle of side $a$. The electric field at the third corner is $E_3$. If $E_0 = \frac{q}{4\pi\varepsilon_0 a^2}$,then which of the following is correct?

The unit of intensity of electric field is