Question

A closely wound solenoid is $60\text{cm}$ long and has $5$ layers of $300$ turns each. The diameter of the solenoid is $1.2\text{cm}$. If the current carried is $5\text{A}$, the magnitude of magnetic field inside the solenoid near its centre is -

• A. $1.57\times {10}^{-2}\text{T}$
• B. $1.57\times {10}^{-4}\text{T}$
• C. $3.14\times {10}^{-3}\text{T}$
• D. $3.14\times {10}^{-2}\text{T}$

Answer 1

The correct option is A $1.57\times {10}^{-2}\text{T}$

Number of turns of wire per metre,

$\frac{5\times 300}{0.6}=2500\text{turns/metre}$

Magnetic field inside a long solenoid is,

$B={\mu }_{0}nI=4\pi \times {10}^{-7}\times 2500\times 5=1.57\times {10}^{-2}\text{T}$