Question

$A$ $90cm$ long solenoid has six layers of windings of $450$ turns each. If the diameter of solenoid is $2.2cm$ and current carried is $6A$ , 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

Answer: (C)

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
$B={\mu }_{0}nI=4\pi \times 10^{-7}\times 3000\times 6$
$=72\pi \times 10^{-4}T$
$=72\pi G$