An electromagnet is a temporary magnet in which a long insulated copper wire is wrapped on a soft iron core in the form of a helix. Thus, an electromagnet is a solenoid having a core of soft iron core at its centre. When electric current in passed through it, it behaves as a magnet because a strong magnetic field is produced in it. An electromagnet is a temporary magnet because it behaves as magnet as long as the current is passed through it. Both the ends of electromagnet behave as north and south pole respectively. The polarity of an electromagnet can be reversed by reversing the flow of current through the coil. When the supply of current is stopped, the magnetism of electromagnet also disappears.
Factors Effecting Strength of Magnetic Field Produced in an Electromagnet
The strength of magnetic field produced in a solenoid depends upon following factors:
1. Strength of Current
The strength of magnetic field produced in a solenoid is directly proportional to the magnitude of current passing through it. Thus, strength of magnetic field increases if the magnitude of current passing through the solenoid is increased.
2. Number of Turns of Wire
Magnetic field can be increased by increasing the number of turns of copper wire in the solenoid.
3. Nature of Core
Magnetic field of a solenoid can be increased by using soft iron as core in the centre of solenoid.
Use of Electromagnets
Following are the uses of electromagnets:
- Electromagnets are used to load and transport scrap iron, steel bars and machine parts.
- Electromagnets are used in electric bells.
- Electromagnets are used in telegraphs to send telegrams.
Differences between a Permanent Magnet and an Electromagnet
| S No. | Permanent Magnet | Electromagnet |
| 1. | A permanent magnet is generally in the form of bar magnet. | An electromagnet is generally in the form of horse shoe. |
| 2. | Permanent magnets are weak magnets. | Electromagnets are stronger than permanent magnets. |
| 3. | The strength of permanent magnets cannot be increased or decreased. | The strength of an electromagnet can be increased or decreased. |
| 4. | The polarity of permanent magnets cannot be reversed. | The polarity of electromagnets can be reversed by reversing the direction of current passing through the coil. |
Test Your Understanding and Answer These Questions:
- What is an electromagnet?
- Write various uses of an electromagnet.
- Describe the construction and working of an electromagnet with the help of a diagram.
- On what factors does the strength of magnetism produced by an electromagnet depend?
- Give differences between an electromagnet and a permanent magnet.