The magnetic dipole moment of a current carrying circular loop of radius \( 7 \) cm is \( 308\,\mu\mathrm{A\,m^{2}} \). The current flowing in the loop is :
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \( 20 \) mA
A current loop is a magnetic dipole with magnetic moment \( m = IA \), so \( I = m/A \).
\( r = 7\,\mathrm{cm} = 7\times10^{-2}\,\mathrm{m} \)
\( \displaystyle A = \pi r^{2} = \frac{22}{7}\times49\times10^{-4} = 1.54\times10^{-2}\,\mathrm{m^{2}} \)
\( m = 308\,\mu\mathrm{A\,m^{2}} = 308\times10^{-6}\,\mathrm{A\,m^{2}} \)
\( \displaystyle I = \frac{m}{A} = \frac{308\times10^{-6}}{1.54\times10^{-2}} = 2\times10^{-2}\,\mathrm{A} = 20\,\mathrm{mA} \)