If the electric field intensity in a fair weather atmosphere is $100 \mathrm{V} {\mathrm{m}}^{-1},$ then the total charge on the earth's surface is (radius of the earth is $6400 \mathrm{km})$

Charge $2 Q$ and $-Q$ are placed as shown in figure. The point at which electric field intensity is zero will be somewhere

Figure shows electric field lines due to a charge configuration, from this we conclude that

Six point charges are placed at the vertices of a hexagon of side $1 \mathrm{m}$ as shown in figure. Net electric field at the centre of the hexagon is

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