Q: A solenoid of length 8 cm has 100 turns in it. If radius of coil is 3 cm and if it is carrying a current of 2 A, find the magnetic induction at a point 4 cm from the end on the axis of the solenoid.

Sol: $\large B = \frac{\mu_0 n i}{2} (sin\alpha + sin\beta)$

$\large B = \frac{4\pi \times 10^{-7}\times 100 \times 2}{2} (\frac{4}{5} + \frac{4}{5})$

= 64 π μT