Question

The energy stored in the magnetic field of solenoid 30 cm long and 3 cm diameter wound with 1000 turns of wire carrying a current of 10 A is

• A. 0.015 J
• B. 0.15 J
• C. 0.5 J
• D. 1.15 J

Answer 1

The correct option is B 0.15 J

Ans : (b)

$L=\frac{{\mu }_0{N}^{2}A}{l}$
$\frac{4\pi \times {1000}^2\times {10}^{-7}\times \pi \times {(\frac{3}{2}\times {10}^{-2})}^2}{30\times {10}^{-2}}$
$=2.96mH$
$E=\frac{1}{2}L{I}^2=\frac{1}{2}\times 2.96\times {10}^{-3}\times {10}^2$
$=0.148J$
$\approx =0.15J$