Two parallel large thin metal sheets have equal surface charge densities $(\sigma = 26.4 \times 10^{-12}\,c/m^2)$ of opposite signs. The electric field between these sheets is

A charged particle of mass $0.003\, gm$ is held stationary in space by placing it in a downward direction of electric field of $6 \times {10^4}\,N/C$. Then the magnitude of the charge is

Charge $Q$ is distributed non-uniformly over a ring of radius $R, P$ is a point on the axis of ring at a distance $3R$ from its centre. Which of the following is a wrong statement.

A half ring of radius $R$ has a charge of $\lambda$ per unit length. The electric force on $1\, C$ charged placed at the centre is

A thin disc of radius $b = 2a$  has a concentric hole of radius $'a'$ in it (see figure). It carries uniform surface charge $'\sigma '$ on it. If the electric field on its axis at height $'h'$ $(h << a)$ from its centre is given as $'Ch'$ then value of $'C'$ is

The three charges $q / 2, q$ and $q / 2$ are placed at the corners $A , B$ and $C$ of a square of side ' $a$ ' as shown in figure. The magnitude of electric field $(E)$ at the comer $D$ of the square, is