Question

A 90 cm long solenoid has six layers of windings of 450 turns each. If the diameter of solenoid is 2.2 cm and current carried is 6 A, then the magnitude of magnetic field inside the solenoid, near its centre is
A. `50 pi G`
B. `60 pi G`
C. `72 pi G`
D. `80 pi G`

Answer 1

Correct Answer - C
For six layers of windings the total number of turns `=6xx450=2700`
Now number of turns per unit length
`n=(N)/(l)=(2700)/(90xx10^(-2))=3000`
Then the field inside the solenoid near the centre
`B=mu_(0)nI=4pi xx10^(-7)xx3000xx6=72pixx10^(-4)T=72piG`