A current of 2 A is passed through a coil of radius 0.5 m having 20 turns. The magnetic moment of the coil is
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → \( 31.4\,\mathrm{A\,m^{2}} \)
A coil of \( N \) turns, each of area \( A \), carrying current \( I \) has a magnetic moment \( m=NIA \). For a circular coil of radius \( r \), the area is \( A=\pi r^2 \).
\( \begin{aligned} A &= \pi r^2 \\ &= 3.14\times(0.5\,\mathrm{m})^2 \\ &= 0.785\,\mathrm{m^{2}} \end{aligned} \)
\( \begin{aligned} m &= NIA \\ &= 20\times2\,\mathrm{A}\times0.785\,\mathrm{m^{2}} \\ &= 31.4\,\mathrm{A\,m^{2}} \end{aligned} \)