A toroid has 500 turns per metre length. If it carries a current of 2 A, the magnetic energy density inside the toroid is

Options

A. 6.28 J `m^(-3)`
B. 0.628 J `m^(-3)`
C. 3.14 J `m^(-3)`
D. 0.314 J `m^(-3)`

Answer

B

Explanation

(b) Energy density = `1/(2mu_(0)) B^(2) = 1/(2mu_(0)) (mu_(0)nI)^(2)`
`rArr 1/2 mu_(0)n^(2)I^(2) = 1/2 xx 4pi xx 10^(-7)xx500xx500xx4`
0.628 J `m^(-3)`