Question

The work done in turning a magnet of magnetic moment M by an angle of 90° form the meridian, is n times the corresponding work done to turn it through an angle of 60⁰. The value of n is given by

• A. 2
• B. 1
• C. 1/2
• D. ¼

Answer 1

Answer: (A)

2

Answer 2

$W = M B ( 1 - \cos \theta )$ ⇒ $\mathrm { W } _ { 0 ^ { \circ } \rightarrow 90 ^ { \circ } } = \mathrm { nx } \left( \mathrm { W } _ { 0 ^ { \circ } \rightarrow 60 ^ { \circ } } \right)$

⇒ $\mathrm { MB } \left( 1 - \cos 90 ^ { \circ } \right) = \mathrm { n } \times \mathrm { MB } \left( 1 - \cos 60 ^ { \circ } \right) \Rightarrow \mathrm { n } = 2$