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.

Length of the solenoid, 1 = 80 cm = 0.8 m

There are five layers of windings of 400 turns each on the solenoid.

Therefore the total number of turns on the solenoid, N = 5 x 400 = 2000

Diameter of the solenoid, D = 1.8 cm = 0.018 m

Current carried by the solenoid, 1 = 8.0 A

Magnitude of the magnetic field inside the solenoid near its centre is given by the relation,

B= μ0NI/l
Where , μ0 = Permeability of free space = 4π x 10⁻⁷ Tm A⁻¹

B = (4π x 10⁻⁷ x 2000 x 8 )/0.8 = 2.5 x 10⁻² T

Hence, the magnitude of the magnetic field inside the solenoid near its centre is 2.512 x 10^-2

T.