A proton and an $\alpha$ particle having equal kinetic energy are projected in a uniform transverse electric field as shown in figure

A small conducting sphere is hanged by an insulating thread between the plates of a parallel plate capacitor as shown in figure. The net force on the sphere is

An electric dipole consists of two opposite charges, each of magnitude $1.0 \mathrm{\mu C}$ separated by a distance of $2.0 \mathrm{cm}$. The dipole is placed in an external electric field of ${10}^5 \mathrm{N} {\mathrm{C}}^{-1}$. The maximum torque on the dipole is