Answer:
The amount of work must be do to rotate the bar magnet is 151.2 J
Explanation:
Given:
Magnetic moment [tex]\mu = 21[/tex] [tex]A. m^{2}[/tex]
Magnetic field [tex]B = 3.6[/tex] T
To find work do to rotate the bar magnet,
From the formula of work done in case of magnetic field,
[tex]U = \mu .B \cos 0 -\mu .B \cos 180[/tex]
Here [tex]\theta[/tex] changes 0 to 180
But [tex]\cos 180 = -1[/tex]
[tex]U = 2\mu B[/tex]
[tex]U = 2 \times 21 \times 3.6[/tex]
[tex]U = 151.2[/tex] J
Therefore, the amount of work must be do to rotate the bar magnet is 151.2 J