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

The correct option is C 72$\pi G$

For six layers of windings the total number of turns $=6\times 450=2700$
Now number of turns per unit length $n=\frac{N}{l}=\frac{2700}{90\times {10}^{-2}}=3000$
Then the field inside the solenoid near the centre
$B={\mu }_{0}nI=4\pi \times {10}^{-7}\times 3000\times 6=72\pi G$