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Answer 1

21. Three ways of demagnetising a magnet are-

• Change the Magnet with High Heat

Heating a magnet causes the electrons inside to spin and generally move to higher energy states, which makes them end up in a position that’s opposed to other electrons nearby.

• Place the Magnet in a Reverse Field

You can also remove the magnetic property of a magnet by placing it in a reversed magnetizing field. This will oppose the object’s magnetism.

• Hammer the Magnet

If you hit the magnet in such a way as to destroy its north and south pole alignment, it will often lose its magnetic properties.

22. way to recognise the magnetic field on earth by we measure magnetic fields because a magnetic field is a vector quantity, there are two aspects we need to measure to describe it; the strength and direction.

The direction is easy to measure. We can use a magnetic compass which lines up with the field. Magnetic compasses have been used for navigation (using the earth's magnetic field) since the 11ᵗʰ century.

Interestingly, measuring the strength is considerably more difficult. Practical magnetometers only came available in the 19ᵗʰ century. Most of these magnetometers work by exploiting the force an electron feels as it moves through a magnetic field.

Very accurate measurement of small magnetic fields has only been practical since the discovery in 1988 of giant magnetoresistance in specially layered materials. This discovery in fundamental physics was quickly applied to the magnetic hard-disk technology used for storing data in computers.

23.A electromagnet is made up out of a coil of wire, a battery, and a chunk of iron. Copper, anonmagnetic material, is wound around the iron, which is called the “core.” While iron can be made into apermanent magnet, the iron core of an electromagnet is not a magnet.

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