In a region, the electric field is given by $\mathbf{E}=(3 \hat{\mathbf{i}}+5 \hat{\mathbf{j}}+7 \hat{\mathbf{k}}) \mathrm{NC}^{-1}$. The electric flux through a surface of area $3 \mathrm{~m}^2$ in $y z$-plane is (in SI units)

The velocity acquired by an electron at rest when subjected to a uniform electric field of potential difference 180 V is

(Mass of electron $=9 \times 10^{-31} \mathrm{~kg}$ and charge of electron $=1.6 \times 10^{-19} \mathrm{C}$ )

Three particles of each charge $q$ are placed at the vertices of an equilateral triangle of side $L$. The work to be done to decrease the side of the triangle to $\frac{L}{2}$ is

If 27 charged water droplets, each of radius $10^{-3} \mathrm{~m}$ and charge $10^{-12} \mathrm{C}$ coalesce to form a single big spherical drop, then the potential of the big drop is