# Square toroid#

A toroid with a square cross section 3.6$$\textrm{ cm}\times$$3.6$$\textrm{ cm}$$ has an inner radius of 21$$\textrm{ cm}$$. It is wound with 415 turns of wire, and it carries a current of 2.6$$\textrm{ A}$$.

## Question Text#

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

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