Presentation on theme: "Do now! Do you know the formulae for Wenesday’s Test? D = m/V p = F/A p = ρhg p 1 V 1 = p 2 V 2 (constant temp and fixed mass) p 1 /T 1 = p 1 /T 1 (constant."— Presentation transcript:
Do now! Do you know the formulae for Wenesday’s Test? D = m/V p = F/A p = ρhg p 1 V 1 = p 2 V 2 (constant temp and fixed mass) p 1 /T 1 = p 1 /T 1 (constant volume and fixed mass) Henry (aged 8¾)
What do you need to know about magnets?
ALL magnets have two poles NORTH seeking pole SOUTH seeking pole
Breaking a magnet produces two magnets! NS NS NNSS
Opposite poles attract and like poles repel
Iron (steel), Cobalt and Nickel
When a magnetic material is close to a magnet, it becomes a magnet itself We say it has induced magnetism N S N S magnet
Hard and Soft Magnetism
Soft Magnetism Pure iron is a soft magnetic material It is easy to magnetise but loses its magnetism easily N S beforeafter Iron nail S N N S Not a magnet N
Hard Magnetism Steel is a hard magnetic material It is harder to magnetise, but keeps its magnetism (it is used to make magnets!) N S beforeafter Steel paper clip N N S It’s a magnet! N S SN
Magnetic fields I wonder if this is a magnetic field?
Magnetic fields 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 closer the field lines are, the stronger the magnetic force felt The arrows show the direction a compass needle would point at that point in the field.
Mind-map Ms Weston will put these slides on a loop and you are going to mind-map them (Colours, drawings, single words)
Plotting magnetic fields
1. Two magnets, opposite poles facing each other 6 cm apart 2. Two magnets, like poles facing each other 6 cm apart 3. Two magnets along side each other, 5 cm apart, opposite poles opposite each other.
Field around a bar magnet
Two bar magnets Strong uniform field
Two bar magnets no field!
Earth’s Magnetic Field N S Remember the North of a compass needle points to the geographic north pole (i.e. the geographic North pole is a magnetic south pole!)