A closely wound solenoid 80 cm long has 5 layers of windings of 400 turns each. The diameter of the solenoid is 1.8 cm .If the current carried is 8.0 A, estimate the magnitude of B inside the solenoid near its centre.

Explanation

l= 80 cm `= 80 xx 10^(-2) m p =5 ,N = 400`
`n=(N)/(l) = (400)/(80 xx 10^(-2)) = 500`
`I = 8 A`
For one turn , `B= mu_(0) nl `
`B = 4pi xx 10^(-7) xx 500 xx 8`
For p turns `= pB = 5 xx 4 pi xx 10^(-7) xx 500 xx 8 = 8 pi xx 10^(-3)`T