A cube of side $b$ has a charge $q$ at each of its vertices. The electric field due to this charge distribution at the centre of this cube will be

Three charges each of magnitude $q$ are placed at the corners of an equilateral triangle, the electrostatic force on the charge placed at the center is (each side of triangle is $L$)

Two charges each of $1\;coulomb$ are at a distance $1\,km$ apart, the force between them is

Force between two identical spheres charged with same charge is $F$. If $50\%$ charge of one sphere is transferred to second sphere then new force will be

A paisa coin is made up of $\mathrm{Al - Mg}$ alloy and weighs $0.75\, g$. It has a square shape and its diagonal measures $17$ $\mathrm{mm}$. It is electrically neutral and contains equal amounts of positive and negative charges.

A particle of charge $-q$ and mass $m$ moves in a circle of radius $r$ around an infinitely long line charge of linear density $+\lambda$. Then time period will be given as

(Consider $k$ as Coulomb's constant)