question_answer

A magnet of total magnetic moment \[{{10}^{-}}^{2}\widehat{i}\,A-{{m}^{2}}\] is placed in a time varying magnetic field, \[B\widehat{i}\left( cos\text{ }\omega t \right)\] where \[B=1\] Tesla and\[\omega =0.125\text{ }rad/s\]. The work done for reversing the direction of the magnetic moment at \[t=1\] second, is- [JEE Main 10-Jan-2019 Morning]

A) 0.014 J

B) 0.028 J

C) 0.01 J

D) 0.007 J

Correct Answer: A

Solution :

[a]

= 1