A solenoid of 1.5 metre length and 4.0 cm diameter posses 10 turn per cm. A current of 5 ampere is flowing through it. The magnetic induction at axis inside the solenoid is

Options

A. `pi xx 10^(-5)T`
B. `2pi xx 10^(-5)T`
C. `3pi xx 10^(-5)T`
D. `4pi xx 10^(-5)T`

Answer

B

Explanation

`n=10` turns/meter and I=5A For the solenoid, `B=mu_0nI=4pi xx 10^(-7)x 10 xx 5 =2pi xx 10^(-5)T`.