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Electromagnet
- A magnet made using electric current
- Works on the magnetic effect of current
- Made of a coil wound on iron
- It is magnetic only while current flows
- Only iron is used for its core
- insulated wire wound on iron
- ends joined to a cell
- iron rod becomes a magnet
- current is switched off
- iron loses its magnetism
- so it stops being a magnet
- Iron is used because it loses magnetism when current stops; steel keeps it and becomes a permanent magnet.
- An electromagnet attracts only magnetic materials — iron, steel, nickel, cobalt.
- It cannot attract wood, plastic, paper, copper or aluminium.
Connect the coil ends to a cell through a switch and switch on the current.
Place steel pins near one end of the nail.
- Current on: pins cling.
- Current off: pins fall.
- Iron nail acts as a magnet.
Advantages and Uses of Electromagnets
- An electromagnet is a temporary magnet
- Its magnetism can be switched on or off
- It can be made very strong
- Used in bells, motors and loudspeakers
- Used in cranes to lift heavy iron
- lifts heavy steel girders
- magnetism switched off to drop them
- used for loading and unloading
- attracts iron from a junk heap
- leaves plastic and copper behind
- separates magnetic materials
- An electromagnet is made stronger by more turns in the coil and more current.
- A permanent magnet cannot be switched off or made so strong.
- Doctors use electromagnets to remove tiny iron particles from the eye.
Name the following: A device which works on the magnetic effect of current.
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Explanation
- An electromagnet works on the magnetic effect of current.
Fill in the blank: The magnet made by using electric current is called an ________.
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Explanation
- It is magnetic only while current flows in its coil.
Fill in the blank: A current carrying coil behaves like a ________. (NCERT Book Question)
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Explanation
- The current in the coil produces a magnetic field, so the coil acts as a magnet.
State whether true or false: A coil becomes an electromagnet only when electric current flows through it.
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Explanation
- The iron core is magnetic only while current flows; switching off removes its magnetism.
State whether true or false: An electromagnet, using a single cell, attracts more iron paper clips than the same electromagnet with a battery of 2 cells. (NCERT Book Question)
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Explanation
- More cells push more current, making the electromagnet stronger, so it attracts more clips.
State whether true or false: An electromagnet does not attract a piece of iron.
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Explanation
- An electromagnet attracts magnetic materials such as iron, steel, nickel and cobalt.
Can you use an electromagnet for separating plastic bags from a garbage heap? Give reason for your answer.
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Explanation
- Plastic is a non-magnetic material.
- An electromagnet attracts only magnetic materials like iron and steel.
- So the plastic bags would not stick to it.
Why do we use iron for making an electromagnet and not steel?
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Explanation
- When current is switched off, iron loses all its magnetism.
- Steel keeps its magnetism and becomes a permanent magnet.
- An electromagnet needs a core whose magnetism can be switched off, so iron is used.
What is an electromagnet? Explain in your own words, how to make an electromagnet.
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Explanation
- Take a thin insulated copper wire and wind it closely around a large iron nail to form a coil.
- Connect the two ends of the coil to a cell through a switch.
- Switch on the current — the iron nail becomes a magnet and attracts steel pins.
- Switch off the current — the nail loses its magnetism and the pins fall.
Two students set up an electromagnet with the same number of turns in the coil. Student A uses a 3V battery, and Student B uses a 6V battery. Whose electromagnet will be stronger? Justify your answer.
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Explanation
- An electromagnet is made stronger by passing more current through the coil.
- A 6V battery drives more current than a 3V battery.
- So the 6V electromagnet has a stronger magnetic effect.
(a) Look at the Figure given. If the compass placed near the coil deflects: (i) Draw an arrow on the diagram to show the path of the electric current. (ii) Explain why the compass needle moves when current flows. (iii) Predict what would happen to the deflection if you reverse the battery terminals. (b) Neha keeps the coil exactly the same as in the diagram but slides the iron nail out, leaving only the coiled wire. Will the coil still deflect the compass? If yes, will the deflection be more or less than before? (NCERT Book Question)
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Explanation
- (a)(i) The arrow shows current flowing from the positive terminal of the battery, around the coil, and back to the negative terminal.
- (a)(ii) The current in the coil produces a magnetic field around it, which acts on the compass needle and turns it.
- (a)(iii) Reversing the battery terminals reverses the current direction, so the magnetic field reverses and the compass needle deflects in the opposite direction.
- (b) Yes, the coil still deflects the compass because a current-carrying coil itself produces a magnetic field. However, the deflection is less than before because the iron nail was making the coil into a stronger electromagnet.
The most suitable material for making the core of an electromagnet is:
- (a) iron
- (b) brass
- (c) aluminium
- (d) steel
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Explanation
- Iron loses its magnetism when current stops, which an electromagnet needs.
