The electric potential ' V ' is given as a function of distance ' $x$ ' (metre) by $V=\left(4 x^2+8 x-3\right) V$. The value of electric field at $x=0.5 \mathrm{~m}$, in $\mathrm{V} / \mathrm{m}$ is

A uniformly charged conducting sphere of diameter 3.5 cm has a surface charge density of $20 \mu \mathrm{Cm}^{-2}$. The total electric flux leaving the surface of the sphere is nearly [permittivity of free space, $\varepsilon_0=8.85 \times 10^{-12} \mathrm{SI}$ unit]

A charged particle of mass ' $m$ ' and charge ' $q$ ' is at rest. It is acce:lerated in a uniform electric field of intensity ' $E$ ' : for time ' $t$ '. The kinetic energy of the particles after time $t$ is