# (a) What is an electromagnet? Describe the construction and working of an electromagnet with the help of a labelled diagram.(b) Explain why, an electromagnet is called a temporary magnet. (c) Explain why, the core of an electromagnet should be of soft iron and not of steel. (d) State the factors on which the strength of an electromagnet depends. How does it depend on these factors? (e) Write some of the important uses of electromagnets.

(a) An electromagnet is a temporary magnet which works when current is passed through it.
It works on the magnetic effect of current. It consists of a long coil of insulated copper wire wrapped around a soft iron core that gets magnetised only when the electric current is passed through the coil.
To make an electromagnet, a soft iron rod is taken and an insulated copper wire is wrapped over it. The two ends of the copper wire are connected to the battery for making an electromagnet.

(b) An electromagnet is called a temporary magnet because its magnetic field depends on the current flowing through its coil. All the magnetism (magnetic field) disappears as soon as the current is switched off.

(c) The core of an electromagnet should be of soft iron and not of steel because soft iron loses all its magnetism when the current in the coil is switched off.
But if steel is used, it does not lose all its magnetism when current is switched off, rather it becomes a permanent magnet.

(d) Strength of an electromagnet depends on the following factors :
1. Number of turns in the coil: By increasing the number of turns in the coil, the strength of an electromagnet can be increased.
2. Current flowing through the coil: By increasing the current flowing through the coil, the strength of an electromagnet can be increased.
3. Length of air gaps between its poles: By reducing the length of air gaps between the poles, the strength of an electromagnet can be increased.

(e) Some of the important uses of electromagnets are as follows :
1. In electrical devices such as in loudspeaker, electric bell, and electric motor.
2. Used by doctors in MRI scanners, and for treating knee pain by using a pulsing electromagnetic field (PEMF).

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Updated on: 10-Oct-2022

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