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An electromagnet can be defined as a soft-iron core that is magnetised temporarily by passing a current through a coil of wire wound on the core.
Principle: It is based on the magnetic effect of electric current.
First step is to gather the materials.
You will need a fairly long iron nail or small iron rod, enameled or insulated copper wire, a pair of wire strippers, switch or key, pins and a battery.
The insulation at both ends of the copper wire must be removed so that it can be connected to a battery. Use the pair of wire strippers to remove the insulation. Wrap the wire tightly and closely around the nail. Wind the wire in one direction only. This is because the direction of the magnetic field depends on the direction of the electric current creating it. If you wrap a part of the wire around the nail in one direction and the other part of the wire in other direction, then the magnetic fields from the different sections are oppositely directed and they cancel out.
Connect the bare ends of the wire to the battery and the switch as shown here.
Place some pins in a box just below the nail and switch on the key. The pins readily jump towards the nail. This shows that the nail has acquired magnetism. That is, the nail is an electromagnet. Switch off the circuit and observe. The pins fall into the box.
When electric current flows through a metal object, the metal object acquires magnetic properties
The metal object loses its magnetic properties when the current ceases to flow through it
The strength of an electromagnet is:
- directly proportional to the number of turns in the solenoid
- directly proportional to the magnitude of the current flowing in the coil
- inversely proportional to the length of the air gap between its poles and
- also depends on the shape of the electromagnet. (Strength of the U-shaped magnet is more than the bar shaped electromagnet
If we use steel (For example, Carbon steel, Chromium steel, Tungsten steel, Nipermag and Alnico) as core material, then it becomes permanent magnet.
Note: Nipermag is an alloy of iron, nickel, aluminium and titanium and Alnico is an alloy of nickel, cobalt, iron and aluminium.
Cranes and lifts use electromagnets to separate and lift large quantities of iron scrap and steel
We find them in electrical devices like electric bells, telegraphs, telephones, loud speakers, electric trains, electric motors and so on
Doctors use weak electromagnets to remove steel splinters from the eye
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