Question

Which of the following actions will decrease the strength of the magnetic field of an electromagnet ?

• A. Using fewer loops of wire per metre in the coil
• B. Decreasing the current in the wire
• C. Removing the iron core
• D. All of the above

Answer 1

Answer: (D)

The magnetic field inside a current carrying solenoid is given by

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

where $n$ is the number of turns per unit length in the solenoid

$I$ is the current through the wire

Hence decreasing current or number of loops per meter would decrease the magnetic field in solenoid.

The iron core being a magnet itself is magnetized hence it contributes flux to the solenoid's flux, hence the magnetic field strength. Hence removing iron core would also decrease magnetic field strength.