Q.
A solenoid of 2.5 metre length and 2.0 cm diameter possesses 10 turns per cm. A current of 0.5
ampere is flowing through it. The magnetic induction at axis inside the solenoid is :
B=μ0nl, where n = number of turns per unit length,
I = current, μ0=4π×10−7TA−1m .
Here n=10cm−1=1000m−1,I = 0.5 A,
Hence B=4π×10−7×1000×0.5
= 2π×10−4 T.