Question

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

• A. uniform over the whole cross-section
• B. maximum onthe outer edge
• C. maximum on the outer edge.
• D. maximum at the centre of cross-section

Answer 1

Answer: (D)

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.