A current 10A is flowing East to West in a long wire kept horizontally in the East - West direction. Find the magnitude and direction of magnetic field in a horizontal plane at a distance of 10 cm North.

Explanation

`l=4.00A,V,1 mm^(3)`
`d=10cm=0.1m, B=(mu_0)/(2 pi r)`
Now magnetic energy stored
=(B^(2)V)/(2(mu_0))=(mu_(0))^(2)(i)^(2))/(4 pi r^2)xx(1)/(2 (mu_0))-xxV`
=(4 pixx10^(-7)xx(4)^2xx1xx10^(-9))/(4xx10^(-2)xx2)`
`=(8)/(pi)xx10^(-14) J`
`=2.55xx10^(-14)J.`