Magnetism


  • Created by: SamFuller
  • Created on: 12-10-18 17:41
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  • Magnetism
    • Poles
      • Magnetic definition - Materials attracted by a magnet.
        • Iron
        • Zinc
        • Nickel
      • North-Seeking Pole definition - The end of a magnetic that points North
      • South-seeking Pole - The end of a magnetic that points South
      • Magnetism on Objects is the greatest near the poles
    • Magnetic Fields
      • Poles
        • Magnetic definition - Materials attracted by a magnet.
          • Iron
          • Zinc
          • Nickel
        • North-Seeking Pole definition - The end of a magnetic that points North
        • South-seeking Pole - The end of a magnetic that points South
        • Magnetism on Objects is the greatest near the poles
      • There is a Magnetic field around a magnet.
        • There is an affect of magnetic materials and other magnets in this area
        • It is convention to draw magnetic field lines coming from North to South
      • Permanent and induced Magnetism
        • A permanent magnet produces its own magnetic field
        • An induced magnet becomes magnetic when it is in a magnetic field
      • The Magnetic field of a straight wire
        • A current in a wire produces a magnetic field
        • Right-hand grip rule: Line your thumb up with the direction of current. The way your hands curl gives you the magnetic field lines direction
        • A cross shows current into the paper
        • A dot shows cureen out of the paper
      • Solenoids
        • A long coil of wire which has a high combined Magnetic Field
        • To increase the strength    1. Increase Current           2. More coils   3. Closer coils                4. Iron core in the centre
      • Magnetic fllux density
        • The number of lines of magnetic flux in a given area
        • Force on a wire = magnetic flux density (teslas) x current x length
        • A magnetic field acts on a wire to repel it.
          • The size of the force depends on the flux density, the sixe of the current
          • Left Hand rule: First finger pints in direction of field lines. Second finger points in direction of current. Thumb gives force direction
      • Direct Current Motors
        • A coil with a current on an axis in a magnet will rotate. This is because current is travelling in alternate directions on each side
          • Kept rotating with a split-ring commutator
      • Induced P.D.
        • When a wire moves through a Magnetic Field it induces a p.d.
        • If the wire is in a creat circuit a current is induced
        • Changing the direction of movement changes the direction of the p.d.
        • This is the generator effect
      • Induced P.D. with Coils
        • Induced P.D.
          • When a wire moves through a Magnetic Field it induces a p.d.
          • If the wire is in a creat circuit a current is induced
          • Changing the direction of movement changes the direction of the p.d.
          • This is the generator effect
        • Moving a magnet near a coil of wire induces a p.d.
        • As the north pole moves towards the coil the current flows in a way the nearest pole becomes a north pole repelling the magnet
        • As the magnet is repelled the direction of cuurent changes and the nearest pole becomes a south pole attracting the magnet back
      • Alternators
        • 1. The coil is vertical. In this position the sides are parallel to the field and there is no p.d.
        • 2. The coils is horizontal. The current cuts through the field at the greatest rate the induced p.d. is at its maximum
        • 3. The coils is ertical again. There is no p.d.
        • 4. The coils is horizontal again. The sides are opposite to 2. and so the p.d. is at the maximum in the alternate direction

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