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Magnetic InductionMagnetic induction is a process where a magnetic material becomes an induced magnet when it is brought near to or in contact with a magnet.


The magnetic material (i.e iron bar) becomes an induced magnet with the end nearer the magnet having opposite pole to that of the magnet. Thus, it is attracted to the magnet as unlike poles attract.
Magnetic induction has to occur before the attraction of magnetic material by a magnet. 
Induced magnetism is a temporary process. If the permanent magnet is removed, the magnetic material will usually lose its induced magnetism.
Top of Page  Types of Magnetic MaterialSoft Magnetic Material
i.e Iron
Hard Magnetic Material
i.e Steel
Easy to be magnetized and demagnetized
Hard to be magnetized and demagnetized
Do not retain its magnetism
Retain its magnetism
To make temporary magnets like electromagnets used in a scrapyard.
To make permanent magnets like magnetic door catch.
The following diagram shows the difference in the magnetic properties of Soft Magnetic Material (Iron) and Hard Magnetic Material (Steel). Top of Page  Example

The diagram shows an aquarium magnetic cleaner which would clean both sides of the fish tank at the same time.  When the magnet A is moved over the outside surface, magnet B would follow it by moving over the inside surface. 
(a) Explain why B follows the movement of A.
(b) Explain why there is a practical limit to the thickness of the fish tank glass for the device to work.
(c) When A and B are placed on opposite sides of a vertical sheet of iron, B remains where it is even when A is removed.  Suggest a reason for this.

(a) Magnet A and B have opposite poles facing each other. Thus, B follows the movement of A as unlike poles attract each other.
(b) Magnetic field strength becomes weaker when the window is too thick, hence the magnets may no longer attract each other strongly and be held in place.
(c) The iron sheet is induced with poles opposite to that of the magnetic pole next to it. Hence attraction still occurs.

Hence attraction happens after magnetic induction occurs.

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