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

Options

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

Answer

C

Explanation

`vec(F)=I(vec(I)xx vec(B))1` or, F = IBlsin `theta`
Since PQ is parallel to the direction of magnetic field, `theta = 0^(@)`.
`F_(PQ)=IlBsin 0^(@)=0`.
Since QR is perpendicular to the direction of magnetic field, `therefore theta = 90^(@)`
`F_(QR)=IlBsin 90^(@)=BIl`.