The magnitude of electric field intensity $E$ is such that, an electron placed in it would experience an electrical force equal to its weight is given by

A charged oil drop is suspended in a uniform field of $3 \times$ $10^{4} V / m$ so that it neither falls nor rises. The charge on the drop will be $.....\times 10^{-18}\; C$

(take the mass of the charge $=9.9 \times 10^{-15} kg$ and $g=10 m / s ^{2}$ )

Find ratio of electric field at point $A$ and $B.$ Infinitely long uniformly charged wire with  linear charge density $\lambda$ is kept along $z-$ axis

Diagram shows symmetrically placed rectangular insulators with uniformly charged distributions of equal magnitude. At the origin, the net field net ${\vec E_{net}}$ is :-

Two point charges $q_{1}$ and $q_{2},$ of magnitude $+10^{-8} \;C$ and $-10^{-8}\; C ,$ respectively, are placed $0.1 \;m$ apart. Calculate the electric fields at points $A, B$ and $C$ shown in Figure

A hollow sphere of charge does not produce an electric field at any