Question

The magnetic field intensity inside a long solenoid is 1 T. If the current per turn of the solenoid winding is 1A, find the number of turns in one meter.

• A. $\frac{1}{4\pi }\times {10}^7$ turns /m
  
• B. $\frac{1}{5\pi }\times {10}^7$ turns /m
  
• C. $\frac{1}{6\pi }\times {10}^7$ turns /m
  
• D. $\frac{1}{7\pi }\times {10}^7$ turns /m
  

Answer 1

The correct option is A $\frac{1}{4\pi }\times {10}^7$ turns /m

We know,

Magnetic field in a solenoid$={\mu }_0\times nI$

Where n=no. of turns per unit length.

To find $n$,

$1=4\pi \times {10}^{-7}\times n\times 1$

$n=\frac{{10}^7}{4\pi }$

Option $\text{A}$ is the correct answer.