A long solenoid is fabricated by closely winding a wire of radius 0.5mm over a cylindrical nonmagnetic frame so that the successive turns nearly touch each other. What would be the magnetic field B at the centre of the solenoid if it carries a current of 5A?
r = 0.5mm, i = 5A, B = μ0ni (for a solenoid)
Width of each turn = 1mm = 10–3m
