A 250-turns recantagular coil of length 2.1 cm and width 1.25 cm carries a current of `85 muA` and subjected to magnetic field of strength `0.85 T`. Work done for rotating the coil by `180^(@)` against the torque is

Options

A. `4.55 muJ`
B. `2.3 muJ`
C. `1.15 muJ`
D. `9.1 muJ`

Answer

D

Explanation

Work = `MB[cos theta_(1) - cos theta_(2)]`
`=MB[cos0^(@) - cos 180^(@)]`
`=NiAB[1-(-1)]`
`=2NiAB`
`=2 xx 250 xx 85 xx 10^(-6) xx 2.1 xx 10^(-2) xx 1.25 xx 10^(-2)`
`=0.12 muJ`