Two objects $A$ and $B$ are charged. Let $q_A=$ charge on $A$ and $q_B=$ charge on $B$, then match column I and column II.

	Column I		Column II
(i)	$q_A=q_B$	a.	Charge transfer by conduction
(ii)	$q_A\ge q_B$	b.	Charging by friction
(iii)	$q_B=\frac{q_A}{2}$	c.	Charging by induction

Four charged particles each having charge $Q=1 \mathrm{C}$ are fixed at the corners of the base ( $A\text{, }B\text{,} C$ and $D$) of a square pyramid with slant length $a\left(AP=BP=PD=PC=a=\sqrt{2} \mathrm{m}\right)$, a charge $-Q$ is fixed at point $P$. A dipole with dipole moment $p=1 \mathrm{C} \mathrm{m}$ is placed at the centre of the base and perpendicular to its plane as shown in figure. Force on the dipole due to the charge particles is $\frac{x}{4\pi {\epsilon }_0}\mathrm{N}$. Find the value of $x$?

A particle having charge that of an electron and mass $1.6\times {10}^{-30} \mathrm{k}\mathrm{g}$ is projected with an initial speed $u$ at an angle ${45}^{\mathrm{o}}$ to the horizontal from the lower plate of a parallel plate capacitor as shown in the figure. The plates are sufficiently long and have separation $2 \mathrm{c}\mathrm{m}$. The maximum value of velocity of particle not to hit the upper plate is $\sqrt{W}\times {10}^6 \mathrm{m} {\mathrm{s}}^{-1}$. Take electric field between the plates as ${10}^3 \mathrm{V} {\mathrm{m}}^{-1}$ directed upward. Find the $W$.