Question

A long solenoid has $50$ turns per meter of its length. If a current of $5\text{A}$ is passed through it, then the magnetic field at the end of the solenoid will be nearly equal to

​​​​​​​$[$0.77 Mark$]$

• A. $0.16\text{mT}$
• B. $1.2\text{mT}$
• C. $1.67\text{mT}$
• D. $4.23\text{mT}$

Answer 1

The correct option is A $0.16\text{mT}$

The magnetic field due to a long solenoid at its end is given by,

$B=\frac{{\mu }_{0}ni}{2}$

Where,
${\mu }_0$ - Permeability of free space
$n$ - Number of turns per unit length
$i$ - Current passing through the solenoid

$\Rightarrow B=\frac{4\pi \times {10}^{-7}\times 50\times 5}{2}=0.157\text{mT}=0.16\text{mT}$