Question

Explain why,

|. An Electro Magnet is called a temporary magnet
ll. The core of an Electro Magnet should be of soft iron
and not of steel
Ill. An A.C source is not used in the Electro Magnet

Answer 1

Explanation:

Because an electro magnet loses its power of attracting after some time or in a proper situation.

Its power of attracting is temporary thats the thing.

Answer 2

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(i) An Electromagnet is called as a temporary magnet, because electromagnet is made up of insulated copper wire wrapped around soft iron, which allows current to flow in it and at that moment iron gains it magnetic properties and when the current is switched off, then there will be no flow of current and hence iron loses its magnetic properties.

Hence it works temporarily as long as electric current flows in a conductor and hence known as temporary magnet.

(ii) Core of an electromagnet should be of soft iron and not of steel because soft iron loses all its magnetism when current in the coil is switched off but steel does not lose its magnetism when the current is stopped.

(iii) The attraction force of an electromagnet is proportional to the square of the magnetic field intensity therefore an AC supply delivers a net attractive force just like DC. It is widely used, for example in some electric door locks, simply because it is cheaper to obtain than DC, requiring just a transformers. Pro: no residual magnetization. Con: annoying buzz while activated.