A rectangular coil of sides 2 cm and 5 cm having 2000 turns and carrying a current of 200 mA is placed in a uniform magnetic field of 5.0 T directed along positive X-axis. The maximum torque experienced by the coil is
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 2 N m
The torque on a current loop in a uniform field is \( \tau = N I A B\sin\theta \), where \( \theta \) is the angle between the field and the normal to the coil. It is maximum for \( \theta = 90^\circ \), when the plane of the coil is parallel to the field.
\( A = 2\,\mathrm{cm} \times 5\,\mathrm{cm} = 10\,\mathrm{cm^2} = 1\times10^{-3}\,\mathrm{m^2} \)
\( I = 200\,\mathrm{mA} = 0.2\,\mathrm{A} \)
\( \displaystyle \tau_{\max} = N I A B = 2000 \times 0.2 \times 1\times10^{-3} \times 5.0 = 2\,\mathrm{N\,m} \)