question_answer

The magnitude of magnetic induction for a current carrying toroid of uniform cross-section is

A)  uniform over the whole cross-section

B)  maximum on the outer edge

C)  maximum on the inner edge

D)  maximum at the centre of cross-section

Correct Answer: A

Solution :

 A toroid can be considered as a ring shaped closed solenoid. Hence, it is like an endless cylindrical solenoid. Consider a toroid having n turns per unit length. Magnetic field at a point P in the figure is given as\[B=\frac{{{\mu }_{0}}NI}{2\pi r}={{\mu }_{0}}nI\]where\[n=\frac{N}{2\pi r}\]. Hence the magnitude of magnetic induction for a current carrying toroid of uniform cross-section is uniform over the whole cross-section.