Question

A coil with magnetic moment 1.48 Aâ‹…m2 is oriented initially with its magnetic moment antiparallel to a uniform magnetic field of magnitude 0.805 T .What is the change in potential energy of the coil when it is rotated 180 degrees, so that its magnetic moment is parallel to the field? Express the answer in joules.

Answer 1

Answer:

-2.3828 J

Explanation:

Magnetic moment = 1.48 Am²

B = Magnetic field = 0.805 T

$\theta_i$ = Initial turns = 180°

$\theta_f$ = Final turns = 360°

Initial in potential energy

$U_i=-mBcos\theta_i\\\Rightarrow U_i=-1.48\times 0.805\times cos180\\\Rightarrow U_i=1.1914\ J$

Final in potential energy

$U_f=-mBcos\theta_f\\\Rightarrow U_f=-1.48\times 0.805\times cos360\\\Rightarrow U_f=-1.1914\ J$

Change potential energy would be

$\Delta U=U_f-U_i\\\Rightarrow \Delta U=-1.1914-1.1914\\\Rightarrow \Delta U=-2.3828\ J$

Change in potential energy is -2.3828 J