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. $6.28 \times 10^{-4} \, T$
• B. $6.28 \times 10^{-1} \, T$
• C. $6.28 \times 10^{-7} \, T$
• D. $6.28 \times 10^{-5} \, T$

Answer 1

Answer: (B)

Length of solenoid $\quad 1=0.4 cm =0.004 m$
Number of turn per unit length $n =\frac{400}{0.004}=10^5$
Magnetic field inside the solenoid $\quad B=\mu_0 nI$
$ \therefore B=4 \pi \times 10^{-7} \times 10^5 \times 5=6.28 \times 10^{-1} T $