AQA GCSE Physics

Revision Notes

7.3.3 Graphs of Potential Difference in the Coil

Higher Tier Only

Graphs of Potential Difference in the Coil

Oscilloscopes

  • A device called an oscilloscope is used to show how the potential difference generated in the coil changes over time
  • It will produce a line, called a trace, on a screen
  • The vertical axis of the trace is the generated potential difference
    • The higher the line, the greater the amount of potential difference induced
  • The horizontal axis of the trace is time
    • This allows the variation in potential difference against time to be shown

Oscilloscope, downloadable IGCSE & GCSE Physics revision notes

Trace of generated potential difference against time on an oscilloscope

Alternating Potential Difference Trace on an Oscilloscope

  • An alternator consists of a rotating magnet next to (or inside) a coil

AC graphs, downloadable IGCSE & GCSE Physics revision notes

Alternating potential difference trace showing the position of the magnet relative to the coil

  • When the magnet is in position 1 the magnetic field lines of the magnet do not cut the coil
    • This means that there is no potential difference induced in the coil
  • When the magnet is in position 2 the magnetic field lines of the magnet are at 90o to the coil
    • This means that there will be maximum potential difference induced in the coil
  • When the magnet is in position 3 the magnetic field lines of the magnet do not cut the coil
    • This means that there is no potential difference induced in the coil
  • When the magnet is in position 4 the magnetic field lines of the magnet are at 90o to the coil
    • This means that there will be maximum potential difference induced in the coil
    • As the poles of the magnet are reversed compared to position 2 the induced potential difference will also be in the opposite direction compared to position 2
    • This means that the trace is negative

Direct Potential Difference Trace on an Oscilloscope

  • A dynamo consists of a coil, which is rotated by a mechanical process, inside a magnetic field

DC graphs, downloadable IGCSE & GCSE Physics revision notes

Direct potential difference trace showing the position of the coil relative to the magnetic field

  • When the coil is in position 1 the magnetic field lines of the magnet do not cut the coil
    • This means that there is no potential difference induced in the coil
  • When the coil  is in position 2 the magnetic field lines of the magnet are at 90o to the coil
    • This means that there will be maximum potential difference induced in the coil
  • When the coil is in position 3 the magnetic field lines of the magnet do not cut the coil
    • This means that there is no potential difference induced in the coil
  • When the coil is in position 4 the magnetic field lines of the magnet are at 90o to the coil
    • This means that there will be maximum potential difference induced in the coil
    • The trace will remain positive because there has been no change to the direction of the magnetic field

Author: Katie

Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.
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