Question

A current of 1.0 A is established in a tigtly wound solenoid of radius 2 cm having 1000 turns / metre. Find the magnetic energy stored in each metre of the solenoid.

Answer 1

Here $1=1.0Ar=2cm,n=1000turns/m$
Magnetic energy stored $=\frac{B^{2}V}{2{\mu }_0}$
[Where B- magnetic field, V - Volume of solenoid]
$=\frac{B^{2}V}{2{\mu }_0}=4\pi \times \frac{{10}^{-7}\times {10}^{-6}\times 1\times \pi \times 4\times {10}^{-4}\times 1}{2}=8{\pi }^2\times {10}^{-5}=78.956\times {10}^{-5}=7.9\times {10}^{-4}J.$