Figure 4 18(b) shows a view of the loop from the AD
end It shows that the torque on the loop tends to rotate
it anticlockwise 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