Question

A magnetic needle has a magnetic moment of 50 e.m.u. cm and weighs 5 g-wt. Where should the point of support be situated relative to its centre of gravity so that the needle maintains a horizontal position in the terrestrial magnetic field in the northern hemisphere? The vertical component of the terrestrial magnetic field is 0.5 oersted.

Answer 1

Answer: x ≅ 0.05 mm.

Explanation:

If x is the distance from the point of suspension to the centre of gravity of the needle (Fig.), the condition of equilibrium of the needle may be written