
Two concentric rings, one of radius and the other of radius , have the charges , and , respectively, as shown in the figure. Find the ratio if a charged particle placed on the axis at is in equilibrium



Important Questions on Coulomb's Law and Electric Field


Four charged particles each having charge are fixed at the corners of the base ( and ) of a square pyramid with slant length , a charge is fixed at point . A dipole with dipole moment 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 . Find the value of ?



A particle having charge that of an electron and mass is projected with an initial speed at an angle 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 . The maximum value of velocity of particle not to hit the upper plate is . Take electric field between the plates as directed upward. Find the .


In the figure shown, find the ratio of the linear charge densities (on semi – infinite straight wire) and (on semi – circular part) that is so that the field at is along direction.

