Find out what factors affect the strength of an electromagnet.

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                Farzana Jalil 10N


The Electromagnet

Aim: To find out what factors affect the strength of an electromagnet.

        In 1831, an English scientist called Michael Faraday and Joseph Henry from USA both separately showed that moving a magnet through coils of wire would generate a current flowing through the wire. If this magnet was thrust into the coil of wires, current flows in one direction but if it was taken out, the direction of current is reversed. This is called electromagnet induction.  

Electromagnets are solenoid (coil of wire) with a piece of iron inside. We say that this iron is ‘soft.’ This means that it changes easily between being magnetised and demagnetised. Electromagnets become a magnet with the use of electric current flowing through them. This means the ‘soft’ iron is ideal for electromagnets, as they are constantly turned on and off.

In contrast, steel is magnetically ‘hard’ so it is therefore suitable for permanent magnets. The material holds on to its magnetism, which means it will be hopeless as an electromagnet but ideal for what a permanent magnet needs.  


The magnetic field around an electromagnet is similar to that around a bar magnet but this one can be made stronger. This means that the ends of the solenoid act like the South Pole and North Pole of a bar magnet, incidentally. When the direction of the current is reversed, the North and South Poles will also reverse.  

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The diagrams above show that if the direction of the current is clock-wise, it is a South Pole and similarly if the direction is anti-clockwise, it is a North Pole.

Today, electromagnets are used for very useful things around the world that would be much harder without the use of them. The photograph below shows a powerful electromagnet lifting a 400-pound block of scrap steel onto a railroad car. The crane on which it is mounted can lift up ...

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