Question

A long solenoid with 20 turns per cm is made to produce a magnetic field of 20 milli Tesla inside the solenoid the necessary current will nearly be

• A. 0.8 ampre
• B. 4.0 ampere
• C. 2.0 ampere
• D. .0 ampere

Answer 1

The correct option is A 0.8 ampre

Number of turns on solenoid $n=20turns/cm=2000turns/m$

Magnetic field $B=20\times {10}^{-3}T$

Current in the solenoid is

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

$=\frac{20\times {10}^{-3}}{4\times 3.14\times {10}^{-7}\times 2000}$

$=0.796A$

$=0.8A$