A toroid of n turns, mean radius R and cross – sectional radius a carries current I. It is placed on a horizontal table taken as xy – plant. Its magnetic moment m

Q: A toroid of n turns, mean radius R and cross – sectional radius a carries current I. It is placed on a horizontal table taken as xy – plant. Its magnetic moment M

(a) Is non- zero and points in the z- direction by symmetry

(b) Points along the axis of the toroid $\vec{M} = M\hat{\phi}$

(c) Is zero, otherwise there would be a field falling as 1/r³ at large distances outside the toroid

(d) Is pointing radially outwards