Question

A wire $PQR$ is bent as shown in figure and is placed in a of uniform magnetic field $B$. The length of $PQ=QR=I$. A current/ amp flows through the wire as shown. The magnitude of the force on $PQ$ and $QR$ will be

• A. BIl,0
• B. 2BIl,0
• C. 0,BIl
• D. 0,0

Answer 1

Answer: (C)

The Lorentz force acting on the curredt carrying conductor in the magnetic field
$F=IBl\sin \theta$
Since, wire $PQ$ is parallel to the direction of magnetic field,
then $\theta =0,$
$\therefore F_{PQ}=IBl\sin 0^{\circ }=0$
Also, wire $QR$ is perpendicular to the direction of magnetic field, then $\theta =90^{\circ }$
$\therefore F_{QR}=IBl\sin 90^{\circ }=IBl$