Transcript electricity & magnetism

ELECTRICITY &
MAGNETISM
BY: Arana Rampersad
Form: 5D
Physics
MAGNETISM
PERMANENT
MAGNETS
MAGNETISM
Magnetism is a force that acts at a distance and
makes a magnet:
 Attract and repel other magnets
 Attract iron, nickel, cobalt and a few other
substances.
Simple activity to identify the poles
of a magnetic dipole
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A dipole is a pair of electrical charges or magnetic
poles of equal magnitude but opposite polarity,
separated by some (usually small) distance. The
direction of the dipole moment corresponds to the
direction from the negative to the positive charge or
from the south to the north pole.
Permanent magnets mean that the material maintains
a magnetic field with no external help. The
characteristic of any magnetic material to do so is called
retentivity.
Simple activity to identify the poles
of a magnetic dipole
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1.
2.
3.
4.
ACTIVITY
SUSPENDING A MAGNET
Have a magnet freely suspended so that it can swing in a horizontal
plane.
Wait until it comes to a rest in an approximate north- south direction
after oscillating to and fro for a short time.
The magnet may be regarded as having a magnetic axis and it would
come to rest with this axis in a vertical plane called the magnetic
meridian.
The pole which points towards the north is called the north seeking or
simply N pole; the other is called the south seeking or S pole.
MAGNETISM
MAGNETIC
FORCES
Simple experiment which show that a
repulsive force exists between like poles
and attractive force between unlike poles
EXPERIMENT: Action of One Magnet on Another.
1.
Suspend a fairly strong magnet.
2.
Put the N pole of the magnet near the N pole of another
magnet; repulsion would occur. (Repulsion would also occur
with two S poles).
3.
Put the N pole of the magnet near the S pole of another
magnet; attraction would occur.
It can be concluded that like poles repel and unlike poles attract.
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Simple experiment which show that
a repulsive force exists between like
poles and attractive force between
unlike poles
Unlike
magnetic
poles
attract.
Like magnetic poles
repel.
Effects of the separation of magnets on
the magnitude of the force between them
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When a strong magnet is placed on a balance
(north pole facing up) and the reading is
recorded, a second magnet is placed directly
above the magnet (north pole facing down).
The balance reading would increase due to the
repulsive forces between the magnets.
If the distance between the magnets gets closer,
the repulsive force would increase.
Effects of the separation of magnets on
the magnitude of the force between them
The force of attraction between magnets
depends:
1. Directly on the strengths of the magnets
2. Inversely on the square of their distance apart.
The closer the two magnets are the greater the
force between them.
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Differentiate between magnetic and
non magnetic materials
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Magnetic Materials
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Non Magnetic Materials
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Materials such as iron, cobalt and
nickel.
Attracted to magnets.
The domains of the magnetic
fields align themselves in an
orderly fashion.
Consists of tiny magnets called
domains which has its own north
and south pole.
Has strong magnetic alloys that
are described as ferromagnetic.
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Materials such as copper, glass,
brass and wood.
Not attracted to magnets.
The domains of the magnetic
fields are randomly aligned and
tends to cancel out.
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How a magnet can attract an
unmagnetized object

A magnet can attract an unmagnetized object by
the process of magnetic induction. This is where
an unmagnetized material for example steel is
place near to or in contact with a pole of a
magnet. When it is removed the object would be
magnetized. This is because the magnetic field
of the magnet is causes the internal molecular
magnets or domains of the steel to align
themselves in the same direction.