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Electromagnet

An electromagnet is a temporary magnet produced by electric current through a coil, usually wound around a soft iron core.

In one line: Current on, magnet on; current off, magnet off.

Practice This Concept

Understand it

An electromagnet works only when current flows.
The soft iron core becomes magnetised quickly and loses magnetism when current is switched off.
That makes an electromagnet very useful in bells, cranes, relays, and electric motors.
Its strength can be changed by increasing current, turns, or core quality.

Example

A scrapyard crane uses a strong electromagnet to lift iron pieces and releases them when the current is switched off.

Formula and rule

Strength of an electromagnet increases with current, number of turns, and use of a soft iron core.

See it worked out

Follow the example line by line, then use the same method on new questions.

Worked example

1If the current in a crane's coil is increased, the electromagnet becomes stronger and can lift more iron scrap.
2When the current is switched off, the scrap is released easily.

Method you can reuse

1Wind insulated wire into a coil.
2Place a soft iron core inside.
3Connect the coil to a battery.
4Current through the coil creates magnetism.
5Switch off current to remove magnetism.

Sketch it in your answer

Draw a coil wound around a soft iron nail with battery connections and labeled north and south poles at the ends.

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

Why is a soft iron core used in an electromagnet instead of steel?

Think first, then show answer

Soft iron is used because it magnetises quickly and loses magnetism quickly when the current stops. This makes the electromagnet temporary and easy to control.

Common wrong answer

The iron core stays magnetised permanently like steel.

Why it loses marks: Soft iron loses magnetism quickly.

Don't mix this up

Students often confuse an electromagnet with a permanent magnet. An electromagnet depends on current and can be switched on or off.

Exam tip

If the question asks for two advantages, mention controllability and temporary magnetism.

Write it in the exam

Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.

How CBSE asks it

Explain construction, working, uses, or advantages of an electromagnet over a permanent magnet.

1
Enough for 1 mark
An electromagnet is a temporary magnet produced by electric current through a coil, usually wound around a soft iron core.
2
Add for 2 marks
Example: A scrapyard crane uses a strong electromagnet to lift iron pieces and releases them when the current is switched off.
3
Add for 3 marks
An electromagnet works only when current flows.

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