37. Electric field at a far away distance r on the axis of a dipole is Eo. What is the electric field at a distance 2r on perpendicular bisector? (1) (2) Eo Eo (3) (4) 16 16 8 38. What is the electric dipole moment of given charge system :- +q 30 +9 (1) 3qa (3) qa/3 a 30 -3q +q (2) 3qa (4) zero 39. Two wires A and B of the same material having radii in the ratio 1 : 2 and carry currents in the ratio 4: 1. The ratio of drift speed of electrons in A and B is:- (1) 16:1 (3) 1:4 (2) 1:16 (4) 4:1 40. Two wires of resistance R and R have temperature coefficient of resistance , and , respectively. These are joined in series. The effective temperature coefficient of resistance is :- (1) (2) 102 2 RR2102 1R1 +2R2 (3) (4) R + R2 R+R