Q: A toroid of non ferromagnetic has core of inner radius 25 cm and outer radius 26 cm. It has 3500 turns & carries a current of 11 A , then find the magnetic field at a point

(i) In the internal cavity of toroid

(ii) At the midpoint of the windings

(iii) At a point which is at a distance of 30cm from the centre of toroid

Sol: (i) B = 0

(ii) $\large B = \mu_0 n i = \mu_0 (\frac{N}{2 \pi r}) i $

$\large B = \frac{\mu_0}{2 \pi} \frac{N i}{r}$

$\large B = 2 \times 10^{-7} \times \frac{3500 \times 11}{51 \times 10^{-2}/2} $

= 29.3 × 10^{-3} T

(iii) B = 0