Module 3 : MAGNETIC FIELD
Lecture 14 : Torque on a Current Loop in a Uniform Magnetic Field

The current enters the branch SR at S marked with $\odot$and reenters from QP at P, marked with $\otimes$. The directions of the forces on the branches SR and QP are shown. The magnitude of the torque about the pivot is

\begin{displaymath}\tau = 2(IbB)\times\frac{q\sin\theta}{2}= IabB\sin\theta= IAB\sin\theta\end{displaymath}

where $A$is the area of the loop.

\includegraphics{fig3.12.eps}

The result above is independent of the shape of the loop. The following example for a circular loop gives an identical result.

Example 4          Exercise 1

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