A conducting loop carrying current 'l' is bent into two halves and placed in mutually perpendicular planes xy and yz planes as shown. A uniform magnetic field `vecB=Bhatj` is existing in the region. The net magnetic torque experienced by the loop is

Options

A. `BIl^(2)(hatk-hati)`
B. `BIl^(2)(hati+hatj)`
C. `BIl^(2)(hatj+hatk)`
D. `BIl^(2)(hati+hatk)`

Answer

A

Explanation

The net magnetic moment of the loop is
`vecM=l l^(2)(hati+hatk)`
The net magnetic torque experienced by the loop is
`vectau=vecMxxvecB`
`=l l^(2)(hati+hatk)xxBhatj`
`vectau=Bl l^(2)(hatk-hati)`