Question

A solenoid $100\text{cm}$ long have $10$ layers of winding of $200$ turns each. If the current carries is $2\text{A}$, then the magnetic field at the centre of the solenoid is nearly?

• A. $1\text{mT}$
• B. $5\text{mT}$
• C. $10\text{mT}$
• D. $3\text{mT}$

Answer 1

The correct option is B $5\text{mT}$

The magnetic field due to a solenoid having $n$ turns and current $i$ flowing through it is, $B={\mu }_{0}ni$

$=4\pi \times {10}^{-7}\times 2000\times 2$
$=16\pi \times {10}^{-4}\text{T}$
$=5\text{mT}$