Transcript Lesson 7 Magnets

Play with your magnets!
ALL magnets have two poles
NORTH seeking pole
SOUTH seeking pole
Breaking a magnet produces two
magnets!
N
N
S
N
S
S
N
S
Opposites attract!
Opposite poles attract and like poles repel
Magnetic materials
Magnetic materials
Iron (steel), Cobalt
and Nickel
Magnetic induction
Magnetic induction
When a magnetic material is close to a
magnet, it becomes a magnet itself
magnet
S
N
S
We say it has induced magnetism
N
Hard and Soft Magnetism
Soft Magnetism
Pure iron is a soft magnetic material
before
S
N
S
after
N
S
NN
Not a
magnet
Iron nail
It is easy to magnetise but loses its
magnetism easily
Hard Magnetism
Steel is a hard magnetic material
before
S
after
N
S
S
N
NN
S
N
It’s a
magnet!
Steel paper
clip
It is harder to magnetise, but keeps its
magnetism (it is used to make magnets!)
Magnetic field
I wonder if this is
a magnetic
field?
Magnetic field
Magnets (and electric currents) produce
magnetic fields around them.
In the magnetic field, another magnet or
magnetic material will experience a magnetic
force.
Magnetic field lines
We can represent the magnetic field
around a magnet using field lines.
Magnetic field lines
The arrows show the direction a compass
needle would point at that point in the field.
Magnetic field lines
The arrows show the direction a compass
needle would point at that point in the field.
The closer the field lines
are, the stronger the
magnetic force felt
Earth’s Magnetic Field
Remember the
North of a compass
needle points to the
geographic north
pole (i.e. the
geographic North
pole is a magnetic
south pole!)
Field around a bar magnet
Two bar magnets
Strong uniform field
Two bar magnets
no field!
That’s it!
Mind-map
Mr Porter is now going to put these slides
on a loop and you’re going to mind-map
them!