Question

A circular coil of 100 turns has an effective radius 0.05m and carries a current of 0.1ampere. How much work is required to turn it in an external magnetic field of 1.5 weber/m² through 180⁰ about an axis perpendicular to the magnetic field. The plane of the coil is initially perpendicular to the magnetic field

• A. 1.8J
• B. 0.236J
• C. 2.4J
• D. 0.236J

Answer 1

Answer: (B)

0.236J

Answer 2

The work done

= $\left( \overset{\rightarrow}{\mu}.\overset{\rightarrow}{B} \right)_{Initial} - \left( \overset{\rightarrow}{\mu}.\overset{\rightarrow}{B} \right)_{Final}$

= $\mu B\left( \cos 0^{0} - \cos 180^{0} \right) = 2\mu B$=$2N\pi a^{2}iB$

= $2 \times 100 \times 3.14 \times (0.05)^{2} \times 0.1 \times 1.5$

=0.236 Joule