2)
In magnitude t = mB sinq
Here ttttt  is restoring torque and q is the angle between m and B An expression for magnetic potential energy can also be obtained on
lines similar to  electrostatic potential energy The magnetic potential energy Um is given by
U
m = ∫τ θd
θ
( )
      =
= −
∫mB
d
mB
sin
cos
θ
θ
θ
      = –m B
(5