A circular coil of 30 turns and radius 8.0 cm carrying a current or 6.0 A is suspend vertically in a uniform horizontal magnetic field of lines make an angle of `60^@` with the normal of the coil. Calculate the magnitude of the counter torque that must be applied to prevent the coil from turning.
b. Whould your answer change, if the circular coil in (a) were replaced by a plannar coil of some irregular shape that encloses the same area ? (All other particulars are also unaltered. )

Explanation

N=30, `r=8 xx 10^(-2) m, I = 6A, B =1 T theta = 60^(@)`
`tau = "BANI" sin 60^(@) =1 xx pi xx (8 xx 10^(-2))^2 xx 30 xx 6 xx sqrt(3)/2 = 3.1 Nm`
b. No change. `because vec tau = NI(vec A xx vec B)`