NCERT Class XII Chapter
Moving Charges and Magnetism
Questions With Solutions

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Question : 8
Total: 28
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.
Solution:  
Total number of turns in 80 cm length of solenoid can be calculated N = 5 × 400 = 2000 turns.
n =
numberofturn
length
=
2000
80×102
= 2500 turns/ m
Magnetic field near centre of long solenoid, B = µ0nI
B = 4π × 107 × 2500 × 8 or B = 8π × 103 T
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