Question

A toroid has a core (non–ferromagnetic) of inner radius 25 cm and outer radius 26 cm, around which 3500 turns of a wire are wound. If the current in the wire is 11 A, what is the magnetic field outside the toroid,inside the core of the toroid and in the empty space surrounded by the toroid.

• A. $0,3\times {10}^{-2}T,0$
• B. $3\times {10}^{-2}T,0,0$
• C. $0,0,3\times {10}^{-2}T$
• D. $3\times {10}^{-2}T,0,3\times {10}^{-1}$

Answer 1

The correct option is A $0,3\times {10}^{-2}T,0$

Inside the core B is finite and rest is zero
$B=\frac{{\mu }_{0}ni}{2\pi r}andr=\frac{r_1+r_2}{2}=\frac{25+26}{2}=25.5=\frac{2\times {10}^{-7}\times 3500\times 11}{25.5\times {10}^{-2}}=\frac{154\times {10}^{-3}}{5-1}=3\times {10}^{-2}T$