# #

A toroid with a square cross section $$\textrm{ cm}\times$$$$\textrm{ cm}$$ has an inner radius of $$\textrm{ cm}$$. It is wound with turns of wire, and it carries a current of $$\textrm{ A}$$.

## Question Text#

What is the strength of the magnetic field at the centre of the square cross section?

$$B=$$ $$\rm\ T$$