Question

Current of $2A$ passing through a coil of $100$ turns gives rise to a magnetic flux of $5\times {10}^{-3}Wb$ per turn. The magnetic energy associated with coil is ______

• A. $5\times {10}^{-3}J$
• B. $5J$
• C. $0.5\times {10}^{-3}J$
• D. $0.5J$

Answer 1

The correct option is D $0.5J$

$\varphi =LI⟹5\times {10}^{-3}=L\times 2\therefore L=\frac{5}{2}\times {10}^{-3}$

$\therefore$Magnetic energy$=U=\frac{1}{2}NL{I}^2=\frac{1}{2}\times 100\times \frac{5}{2}\times {10}^{-3}\times 4=0.5J$