Question

State whether the following statement is true or false.
An electromagnet is a temporary magnet.
A. True
B. False

Answer 1

Hint: It is observed that when current is passed through a wire, a magnetic field is created around it. When the flow of current stops, the magnetic field also disappears. This is the principle used in making electromagnets using circular coils of coated copper wire called a solenoid.

Complete solution Step-by-Step:
Magnetism and electricity are related to each other. Flowing electric charges give rise to magnetic fields. If we pass current in a straight conducting wire, then a circular magnetic force field appears around it, which can attract magnetic materials like iron and cobalt.

To increase the strength of this magnetic force we can use coated copper wire and wind it in circular fashion. In this way the magnetic field inside the winding will be stronger compared to outside. To further direct and strengthen the field, soft iron can be placed in this solenoid. This will behave as a bar magnet and is called an electromagnet, because the iron becomes magnetised due to the presence of electricity and can attract other magnetic materials.

The direction of the north and south pole of the electromagnet depends on the direction of current.

But, as soon as the flow of electricity is stopped, the soft iron loses all its magnetic field strength. It can no longer attract materials made of iron. Thus, the magnetisation developed in the soft iron bar was temporary and the effect lasts only as long as the current is flowing in the wire around it.

Hence, an electromagnet is a temporary magnet. Correct option is : A - True

Note:
1. Electromagnet can be turned on and off at will. Also, the polarity can be reversed just by changing the direction of current in the solenoid. Thus, electromagnets are main components of machinery such as cranes and MRI.
2. The strength of the magnetic field produced by electromagnet depends on the amount of current flowing in the wire as well as the number of circular turns of solenoid. Thus, by increasing the current or number of turns, magnetic fields much more powerful than natural magnets can be produced.