Question

A long solenoid is formed by the winding $20turns/cm$. What will be the current necessary to produce a magnetic field of $20millitesla$ inside the solenoid?
($\frac{{\mu }_0}{4\pi }={10}^{-7}tesla-meter/ampere$)

• A. $8.0A$
• B. $4.0A$
• C. $2.0A$
• D. $1.0A$

Answer 1

Answer: (A)

$8.0A$

The magnetic field due to a long solenoid is:

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

$\Rightarrow i=\frac{B}{{\mu }_{0}n}$

$=\frac{20\times {10}^{-3}}{4\pi \times {10}^{-7}\times 20\times 100}$

$=7.9amp=8amp$