A thin conducting ring of radius R is given a charge +Q. The electric field at the centre O of the ring due to the charge on the part AKB of the ring is E. The electric field at the centre due to the charge on the part ACDB of the ring is

Charges +q and $$-$$q are placed at points A and B respectively which are a distance 2L apart, C is the midnight between A and B. The work done in moving a charge + Q along the semicircle CRD is

A hollow cylinder has a charge q coulomb within it. If $$f$$ is the electric flux in units of voltmeter associated with the curved surface B, the flux linked with the plane surface A in units of V-m will be

Three point charges +q, $$-$$ 2q and + q are placed at points (x = 0, y = a, z = 0), (x = 0, y = 0, z = 0) and (x = $$a$$, y = 0, z = 0) respectively. The magnitude and direction of the electric dipole moment vector of this charge assembly are