Question

A long solenoid is formed by the winding 20 turns/cm. What will be the current necessary to produce a magnetic field of 20 millitesla inside the solenoid?
($\frac{μ_0}{4π}=10^{−7}$ tesla−meter/ampere)

• A. 4.0 A
• B. 1.0 A
• C. 8.0 A
• D. 2.0 A
• E. 9.0 A

Answer 1

Answer: (C)

8.0 A

Answer 2

The correct option is (C): 8.0 A
The magnetic field due to a long solenoid is:
B=μoni
=$i=\frac{B}{μ_ON}$
$=\frac{20\times10^{-3}}{4\pi\times10^{-7}\times20\times100}$
=7.9 A= 8 amp