A solenoid 1.5 m long and 0.4 cm in diameter possesses 10 turns per cm length. A current of 5 A falls through it. The magnetic field at the axis inside the solenoid is

Options

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

Answer

A

Explanation

Magnetic field at the axis inside the solenoid
`b=mu_(0)nI`
`n=10 cm^(-1)=1000 m^(-1)`
`therefore B = 4pi xx 10^(-7)xx1000xx5=2pi xx 10^(-3)T`.