Question

If current in the core decreases, the strength of the magnetic field

• A. decreases
• B. increases
• C. sometimes decreases and sometimes increases
• D. remains unchanged

Answer 1

The correct option is A decreases

The magnetic field inside a solenoid is given by

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

where $n$ is the number of turns in coil per unit lenght,

$I$ is the current through the solenoid

Hence when the current in the solenoid decreases, the strength of magnetic field $B$ also decreases.