Temporary magnets are those which become very sirong magnets quickiy and loose it as soon as

the magnetizing force is removed. Soft iron and alloys of nickel, manganese and silicon (e.

Stalloy, Pemalloy, Mu-metal etc.) are used for making electromagnets. These are used in elec-

tric bell, telephone receiver, magnetic relays, etc.

as

What is force?

Force 1s the ph

sI unit 1s Newto

phy-

How can two ve

By using (1) Lav

nents. (1V) Head

What is an electromagnet?

It 1s a temporary magnet which can be made by winding coils in opposite directions round two

soft iron cores, whose lower ends become magnetic poles on passing current. When the current is

Switched off, the magnetism in the soft iron disappears.

Describe law of

f two inclined fe

then the diagona

Why do we use soft iron for making an electromagnet?

Because soft iron is more easily magnetized than steel (iron with carbon), and looses its magnet

Sm more easily.

What is the law

If P and are

p+Q+2PQ

What are ferrites and where are they used?

Strongly magnetic materials are called ferrites. They are chemical combination of zinc oxide

with ferric oxide (Fe,O3). Ferrites can be magnetized strongly and are not demagnetized easily

once they are magnetized.

Ferrite rods (black and hard) are used in aerials of transistor receivers, for reception of micro- It is the combinec

waves and in computer memory unit.

A fine iron oxide powder is used to coat the tapes used in tape-recorders. Magnetic ink iS used on

cheques for bank's computer.

What is a resulta

What is an equil

It is the vector tha

is equal and oppo

What are the three kinds of magnetic materials?

) Ferromagnetic Substances: These are the substances which are attracted strongly by a mag-What is the func

net. Five elements (Fe, Co, Ni, Gd and Dy) are ferro magnetic, as are many alloys (includ-

ing steel).

ii) Paramagnetic Substances: