Question

 A current of 2 A flowing through a coil of 100 turns gives rise to a magnetic flux of 5 × 10−5 Wb per turn. Calculate the magnetic energy associated with the coil

Answer 1

$W=\frac{n\Phi I}2=\frac{100\cdot 5\cdot 10^{-5}\cdot 2}2=5~mJ.$