Question

A solenoid 4 cm in diameter and 20 cm long has 250 turns and carries a current of 15 a calculate the flux through the surface of the disc of 10 cm radius that it is positioned and centered on the axis of the solenoid.

Answer 1

magnetic field at centre = n x υ₀ x I = 250 x 4π x 10⁻⁷
x 15
B = 15π x 10⁻⁴

hence flux ,
Φ = B.A.Cosθ
= 15π x10⁻⁴ x (0.1)² ( Considering θ to be 0 as

= 15π x 10⁻⁶ Wb you've not mentioned it)