Question

A solenoid has length 0.4 cm, radius 1 cm and 400 turns of wire. If a current of 5 A is passed through this solenoid, what is the magnetic field inside the solenoid?

• A. $6.28\times {10}^{-1}T$
• B. $6.28\times {10}^{-3}T$
• C. $6.28\times {10}^{-2}T$
• D. $6.28\times {10}^{-6}T$

Answer 1

The correct option is A $6.28\times {10}^{-1}T$

Length of solenoid $l=0.4$ cm $=0.004$ m

Number of turn per unit length $n=\frac{400}{0.004}={10}^5$

Magnetic field inside the solenoid $B={\mu }_{o}nI$

$\therefore$ $B=4\pi \times {10}^{-7}\times {10}^5\times 5=6.28\times {10}^{-1}$ $T$