Question

The effective length of a magnet is 31.4 cm and its pole strength is 0.5 A.m. The magnetic moment, if it is bent in the form of a semicircle will be _______ Amp.m². 

(a) 0.1 

(b) 0.01 

(c) 0.2 

(d) 1.2

Answer 1

The correct option (a) 0.1

Explanation:

Magnetic moment = M = pole strength × effective length

= 0.5 × 31.4 × 10^–2

= 15.7 × 10^–2 Am²

when bent in semicircle, new magnetic moment = M' = (2M/π)

∴ M' = [(2 × 15.7 × 10^–2)/(3.14)] = 0.1 Am²