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A toroid of $n$ turns, mean radius $\mathrm{R}$ and cross-sectional radius a carries current I. It is placed on a horizontal table taken as $x y$-plane. Its magnetic moment $m$
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is zero, otherwise there would be a field falling as $\frac{1}{r^3}$ at large distances outside the toroid
is zero, otherwise there would be a field falling as $\frac{1}{r^3}$ at large distances outside the toroid
Toroid is a hollow circular ring on which a large number of turns of a wire are closely wound. Thus, in this case magnetic field is only confined inside the body of toroid.
So no magnetic field outside the toroid and magnetic field only inside the toroid.
In case of toroid, the magnetic field is in the form of concentric magnetic lines of force and there is no magnetic field outside the body of toroid. This is because the loop encloses no current. Thus, the magnetic moment of toroid is zero.
In other case, if we take $r$ as a large distance outside the toroid, then $m \propto \frac{1}{r^3}$. Which is not possible.
So no magnetic field outside the toroid and magnetic field only inside the toroid.
In case of toroid, the magnetic field is in the form of concentric magnetic lines of force and there is no magnetic field outside the body of toroid. This is because the loop encloses no current. Thus, the magnetic moment of toroid is zero.
In other case, if we take $r$ as a large distance outside the toroid, then $m \propto \frac{1}{r^3}$. Which is not possible.
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