A long solenoid with 40 turns per cm carries a current of 1A. The magnetic energy stored per unit volume is __________`J//m^(3)`

Options

A. `3.2pi`
B. `32pi`
C. `1.6pi`
D. `64pi`

Answer

A

Explanation

`n=(40)/((10))=4xx10` /metre, B (long solenoid) = `munI`
Energy per unit volume = `(1)/(2mu_(0))B=(1)/(2mu_(0))(munI)=(n^(2)I^(2))/(2)`
`=(4pixx10^(7)xx(4xx10^(3))xx(1))/(2)`
`=32pixx10^(-1)=3.2piJm^(-3)`