Question

A toroid of $n$ turns, mean radius $R$ and crosssectional radius a carries current $I$. It is placed on a horizontal table taken as $x-y$ plane. Its magnetic moment $\overrightarrow{M}$

• A. is non-zero and points in the z-direction by symmetry
• B. points along the axis of the toroid $\left(\overrightarrow{M} = M \hat{\phi}\right)$
• C. is zero, otherwise there would be a field falling as $\frac{1}{r^{3}}$ at large distances outside the toroid
• D. is pointing radially outwards

Answer 1

Answer: (C)

is zero, otherwise there would be a field falling as $\frac{1}{r^{3}}$ at large distances outside the toroid

Answer 2

In a toroid magnetic field is only confined inside the body of toroid in the form of concentric magnetic lines of force and outside the toroid magnetic field is zero.