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 x-y plane. Its magnetic moment m
A. is non-zero and points in the z-direction by symmetry.
B. points along the axis of the toroid .
C. is zero, otherwise, there would be a field falling as at large distances outside the toroid.
D. is pointing radially outwards.
The answer is the option (c)
The toroid is a ring-shaped solenoid, and the magnetic field is confined inside the body of the toroid. The magnetic moment inside and outside the toroid is zero as there is no current enclosed in those spaces.