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Electrical Quantities

Edexcel AS-level PhysicsTopic 5 of 1118 lessons

Revision notes for Electrical Quantities in Edexcel Physics (8PH0). Read the start of any lesson here, then sign in free for the whole lesson, the R.E.C.I.P.E. recall steps and the quiz.

  1. Electric ChargeSome particles have an electric charge.
  2. Electric CurrentCurrent is the rate of flow of charge.
  3. Charge CarriersThe movement of charge carriers forms an electric current.
  4. Electromotive Force e.m.f.The electromotive force or e.m.f. is a measure of the work done per unit charge by the cell.
  5. Potential DifferenceThe potential difference is another measurement of voltage.
  6. The Electron VoltThe electron volt is a small unit of energy usually used for sub-atomic particles.
  7. ResistanceThe movement of electrons through a circuit is caused by the force the emf generates.
  8. Ohm's LawFor some components the current is directly proportional to the potential difference providing the temperature remains constant.
  9. Example QuestionA resistor is connected to a power supply so that the potential difference across it is 6.0 V.
  10. Current-Voltage GraphsFor a filament lamp for small voltages the current is proportional to the potential difference and the filament lamp acts as an ohmic conductor.
  11. ResistivityResistivity is a property of a type of material.
  12. Conduction and Drift VelocityMetals consist of a lattice of positive metal ions surrounded by a sea of delocalised electrons.
  13. Resistance and TemperatureElectrons are constantly colliding with atoms in the metal's lattice and with other electrons.
  14. SemiconductorsSemiconductors only have a small number of delocalised electrons that are able to act as charge carriers.
  15. Current-Voltage Graph for DiodesThe diode conducts only in the forward direction (forward bias) as long as a threshold p.d. of 0.6V is exceeded.
  16. Current-Voltage Graph for Thermistors and LDRsThermistors are made of semiconductor materials.
  17. InsulatorsWith insulators there is a larger energy gap between the conduction band and the valence band and there are virtually no conduction electrons.
  18. SuperconductivityReducing the temperature of material reduces the resistance because the atoms move less and there are fewer collisions between the electrons and the…

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