Electromagnet and its Uses:
The fact that a magnetic field is produced when an electric current is passed through a coil has been utilized in the construction of electromagnets. It has been found that the magnetic effect of a coil or solenoid is greatly increased if a core of soft iron is introduced inside the coil. The combination of coil and magnetic core is, therefore, called an electromagnet.
Commercial electromagnets are made by winding a large number of terms of insulated wire on a soft iron core. Magnetic effects are produced when a current is switched on in the coil.
The strength of an electromagnet depends on three factors:
- Number of turns.
- Strength of the current.
- Nature of the core.
We know that the magnetic effect of a coil depends on the ampere-turns of the coil. Ampere-turns are the result obtained by multiplying the number of turns with the current flowing in the coil. Thus, 1A current flowing in 20 turns has the same effect as 2A current flowing in 10 turns. The strength of the magnetic field is greatly increased by inserting a core of some magnetic material, like soft iron, inside the coil.
Electromagnets can be made in different shapes. In the U-shaped electromagnet, insulated copper wire is wound in opposite directions on the two arms as shown above.
Uses of Electromagnet:
Electromagnets are usually temporary magnets. They lose their magnetism as soon as the current in them is switched off. An electromagnet, therefore, allows us to turn the magnetic field on or off, merely by the flick of a switch. Electromagnets are hence used in a great many devices.
(1) For Lifting- Electromagnets are used to “lift” magnetic materials, such as scrap iron, iron sheets, cast iron articles, etc. Lifting magnets are usually equipped with portable d.c. generators which supply the electric current. The so-called “lifting electromagnets” do not lift the load, they merely hold it fast while a motor-driven crane lifts both the electromagnet and the load.
(2) In Hospitals- Electromagnets are used in hospitals to remove iron fragments from the eye and the flesh.
(3) As Magnetic Separators- In industry, magnetic separators using electromagnets are used to sort magnetic ore from non-magnetic ore, scrap iron from coal, iron particles from sand, nails and iron pieces from fields, etc.
(4) In Electromagnetic Devices- Electromagnets form an essential part of the construction of electric bells, telephone receivers, dynamos, motors, electric fans, etc.
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