Question

A closely wound solenoid 80 cm long has 5 layers of windings of 400 turns each. The diameter of the solenoid is 1.8 cm. If the current carried is 8.0 A, estimate the magnitude of B inside the solenoid near its centre.

Answer 1

Length of the solenoid, l = 80 cm = 0.8 m 
There are five layers of windings of 400 turns each on the solenoid. 
∴ Total number of turns on the solenoid, N = 5 × 400 = 2000 
Diameter of the solenoid, D = 1.8 cm = 0.018 m 
Current carried by the solenoid, I = 8.0 A 
Magnitude of the magnetic field inside the solenoid near its centre is given by the relation

Where, 0 = Permeability of free space = 4π × 10^–7 T m A^–1

Hence, the magnitude of the magnetic field inside the solenoid near its centre is 2.512 × 10^–2 T.