Question

A magnet of magnetic moment 20 C.G.S. units is freely suspended in a uniform magnetic field of intensity 0.3 C.G.S. units. The amount of work done in deflecting it by an angle of 30° in C.G.S. units is

• A. 6
• B. $3 \sqrt { 3 }$
• C. $3 ( 2 - \sqrt { 3 } )$
• D. $3$

Answer 1

Answer: (C)

$3 ( 2 - \sqrt { 3 } )$

Answer 2

$\mathrm { W } = \mathrm { MB } ( 1 - \cos \theta ) \Rightarrow \mathrm { W } = 20 \times 0.3 \left( 1 - \cos 30 ^ { \circ } \right) = 3 ( 2 - \sqrt { 3 } )$