To measure the magnetic moment of a bar magnet, one may use (a) a tangent galvanometer (b) a deflection galvanometer if the earth' horizontal field is known (c) an oscillation magnetometer if the earth' horizontal field is known (d) both deflection and oscillation magnetometer if the earth'* horizontal field is not known.
(b) a deflection galvanometer if the earth'* horizontal field is known
(c) an oscillation magnetometer if the earth'* horizontal field is known
(d) both deflection and oscillation magnetometer if the earth'* horizontal field is not known.
