Science 8 L5.1

The First Magnets

•Magnetite – a naturally-occurring mineral

•It attracts others pieces of magnetite and
iron

•If a piece of iron was rubbed with
magnetite, it acted like magnetite

Compasses

•Sailors found out that, if you
rubbed an iron needle on
magnetite and placed it on the
surface of water, it pointed
north

•These were likely the first
compasses
•But why did they point north?

•And how do magnets work?

Magnets

Magnet – a piece of magnetite, iron, or steel that attracts other
objects made of iron or steel

Magnets can attract things like nails, paper clips, etc.

Magnets can also attract or repel other magnets

Magnetic Poles

WHY DO

MAGNETS

WORK?

There’s just one
question, though…

Magnetic Fields

•The force exerted through a magnet, that
affects iron or other magnets at a distance

•The field bends and connects the two
poles

•The field is in all three dimensions, not just
on a flat surface

•The closer the lines are, the stronger the
field is in that area

HOW MAGNETIC FIELDS ATTRACT

AND REPEL

The Atom!

+

-

Nucleus

Electron

•The electron is orbiting
around its nucleus

•It’s also rotating around
its own axis

•Each electron produces
its own magnetic field

•Each atom becomes a
tiny magnet

Magnetic
Domain

•In iron, each atom’s magnetic field can point
in the same direction

•All of those fields add up to one larger field

•The iron becomes magnetic

•Magnetic Domain – A group of atoms with
all of the magnetic fields pointing in the
same direction

Finally, A Definition For “Magnet”

Magnets and iron have small magnetic domains, each with
their own magnetic fields

Those domains line up and produce one big field, which
makes the material magnetic

In magnets, this field is permanent

In iron, it is temporary

What is a magnet?

• A magnet is an object which attracts metals.

• Metals like copper, aluminium, nickel, iron etc. are attracted by magnets.

• A magnet makes a magnetic field around it and due to that magnetic field, the metals are attracted towards it.

• There are three types of magnets, we will know more about them in the next session.

Types of Magnets

There are three types of magnets-

1-Temporary Magnets-Magnets which when placed in a strong magnetic field become a permanent magnet, but when they are moved away from the magnetic field, it loses its magnetic force.

2-Permanent Magnets-Magnets which produce their own magnetic field and attract metals are called permanent magnets.

3-Electromagnets-Electromagnets are the magnets which make their own magnetic field using electricity. An electromagnet usually consist of wire wound into a coil. A current through the wire creates a magnetic field which is concentrated in the hole, denoting the centre of the coil.

Introduction To Magnetism

In this session, we will know about magnetism.

Magnetism

• Magnetism is a class of physical phenomena that are mediated by magnetic fields.

• Electric currents and the magnetic moments of elementary particles give rise to a magnetic field, which acts on other currents and magnetic moments.

• Magnetism is one aspect of the combined phenomenon of electromagnetism

Magnetism

• Magnetism is a class of physical phenomena that are mediated by magnetic fields.

• Electric currents and the magnetic moments of elementary particles give rise to a magnetic field, which acts on other currents and magnetic moments.

• Magnetism is one aspect of the combined phenomenon of electromagnetism

Can all objects be attracted by magnets?

In this session, we will know that whether all objects can be attracted to magnets or not.

Can all objects be attracted to magnets?

• No, all objects cannot be attracted to magnets.

• Only metals can be attracted from magnets.

• Metals can be attracted to magnets because they also have some magnetic power in them.

Test For Magnetism

• An unmagnetised magnet material would be attracted to both poles.

• Magnetism can work over a distance and magnets can exert a force (push or pull) on objects without making contact with them.

Demagnetisation of a magnet

• The demagnetisation of a magnet includes the following processes-

• Heating past the Curie point.

• Applying a strong magnetic field.

• Applying alternate current, or,

• Hammering the metal.