Magnetism basic, physics

1. Magnetism

2. Magnetism – force of attraction or repulsion
between two substances.
Magnetite or Lodestone – the first known rocks
with magnetic substances.

3. Ancient Sailors used Magnetite as compass.
They tie a piece of magnetite to a string and
suspends. It points to the North-South
direction.

4. Atoms have magnetic properties
- the spinning, and electric charge of electrons
make atoms a magnet.

5. Magnetic Domains – are regions where atoms
are aligned uniformly. They are like miniature
magnets. Groups of atoms that act like one
tiny magnets.

6. Question:
If atoms are miniature magnets, and objects around
us has a potential to be magnets why cannot
ordinary objects attract or repulse objects?

7. When magnetic domains are not aligned
uniformly their magnetic force is very weak.
But when they are aligned in the same direction,
their magnetic force becomes stronger.

8. How do you turn neutral objects into objects
with strong magnetic force?
Use another magnet or use electricity to induce
magnetism.

9. Exposure to magnetic fields aligns magnetic
domains uniformly.

10. Question:
If you need a magnet to make another magnet
where did the first magnet come from?
The first magnet is our planet.

11. Natural Formation of Magnets
- Volcanoes erupt which brings magma (molten
Rock) into earths surface.
- Magma contains ferric (iron) materials.
- Iron containing magma become magnetized
through contact with earth’s magnetic field.

12. Properties of Magnets
Magnets are Dipoles (two poles). North-South
poles

13. Magnetic force at the poles is stronger than that
in the middle.
Like poles repel each other, unlike poles attract
each other.

14. When magnets are suspended freely it aligns its
south-north poles to the North – South poles
of earth.

15. Magnets attract Ferromagnetic materials
Ferromagnetic – metals (like iron) which are
attracted to magnets.
Note: Not all metals are attracted to magnets (
copper and aluminium are not attracted to
magnets)
Ferromagnetic Materials: iron, steel, and alloys.

16. Classification of Magnets
Paramagnets – substances which react to
magnetic field but do not retain display
magnetic properties when the magnetic field
is removed.
Examples: oxygen, calcium, sodium, aluminium

17. • Diamagnets – objects which are repelled by
strong magnetic fields. It does not retain its
magnetic property when magnetic field is
removed.
Example: water, carbon, bismuth

18. Ferromagnets – objects which react strongly to
magnetic fields. They retain their magnetic
characteristics even when the magnetic field is
removed.
Example: iron, steel, alloy.

19. Anti-ferromagnets – they react very weakly to
magnetic fields.
Example: Chromium