Question

A solenoid of 1.5 m length and 4.0 cm diameter has 10 turns per cm. A current of 5 A is flowing through it.The magnetic field induction at axis inside the solenoid is:

• A. $2\pi \times {10}^{-4}T$
• B. $2\pi \times {10}^{-3}T$
• C. $20\pi G$
• D. $2\pi G$

Answer 1

The correct option is B $2\pi \times {10}^{-3}T$

Given: N=10 turns per cm, i=5A

Solution: As we know that the formula of magnetic field inside the solenoid is :

$B={\mu }_{0}ni=\frac{{\mu }_{0}ni}{l}=\frac{4\pi \times {10}^{-7}\times 10\times 5}{{10}^{-2}}=2\pi \times {10}^{{}^{-3}}T$

Hence the correct answer is B