This torque is (in magnitude),
1
2
2
2
a
a
F
F
τ =
+
(
)
2
2
a
a
IbB
IbB
I ab B
=
+
=
    = I A B
(4 26)
where A = ab is the area of the rectangle We next consider the case when the plane of the loop,
is not along the magnetic field, but makes an angle with
it We take the angle between the field and the normal to
the coil to be angle q (The previous case corresponds to
q = p/2)