Transcript magnetic needle

PHY-AP -11 Magnetism
By
Squadron Leader Zahid Mir
CS&IT Department , Superior University
Magnets
• Magnets have been known for
centuries.
• The Chinese and Greeks knew
about the “magical” properties of
magnets.
• The ancient Greeks used a stone
substance called “magnetite” (an
oxide of iron). They discovered
that the stone always pointed in
the same direction. Later, stones of
magnetite called “lodestones” were
used in navigation.
• William Gilbert, an English physician, first proposed in
1600 that the earth itself is a magnet, and he predicted
that the Earth would be found to have magnetic poles.
What is Magnetism?
• Magnetism is the force of attraction or
repulsion of a magnetic material due to
the arrangement of its atoms, particularly
its electrons.
Magnetic Needle
• A magnetized steel rod that,
when adjusted to swing in a
horizontal plane, indicates
the direction of the Earth’s
magnetic field.
• The “RED” end always point
towards the geographical
north, also known as
“North-Seeking Pole”
Magnetic Interactions
• One magnet set up a magnetic field and the
other magnet respond to that magnetic field.
Magnet
Field
Magnet
Magnetic Field of a Bar Magnet
Magnetism First Law
Like poles repel each other while unlike poles
attract each other.
Magnetic fields due to Current
• Compass needle indicates the direction of
magnetic field around a current carrying wire.
• Magnetic field vanishes when current is
switched off.
This shows a direct link between electricity
and magnetism