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Direct Current Circuits

AQA AS-level PhysicsTopic 14 of 1415 lessons

Revision notes for Direct Current Circuits in AQA Physics (7407). Every lesson in BrainCake comes with R.E.C.I.P.E. recall steps, a quick check and spaced reviews.

  1. Current RulesAt any junction in a circuit the total current leaving the junction is equal to the total current entering the junction.
  2. Potential Difference RulesThe potential difference rules come from the conservation of energy.
  3. Resistors in SeriesV = V1 + V2 Resistors in series pass the same current.
  4. Resistors in ParallelThe reciprocal of the total resistance of the circuit is equal to the sum of the reciprocals of all the resistors in the circuit.
  5. Resistance HeatingThe heating effect of a current is due to the resistance of the circuit.
  6. Internal ResistanceThe internal resistance of a source is the loss of potential difference per unit current in the source when current passes through the source.
  7. PowerThe power supplied by the cell is equal to Iε.
  8. Measuring Internal ResistanceThe p.d. across the terminals of a cell can be measured using a high resistance voltmeter when the cell is in a circuit and current is flowing.
  9. Cells in SeriesIf the cells are connected in the same direction, the net e.m.f. is the sum of the individual e.m.f. s If the cells are connected in opposite…
  10. Cells In ParallelIf the cells are connected in the same direction, the net e.m.f. is equal to each individual e.m.f. s If the cells are connected in opposite…
  11. Diodes in CircuitsA diode that is forward biased has a p.d. of about 0.6V (the threshold voltage) across it whenever a current flows through it.
  12. The Potential Divider - Fixed p.d.A potential divider consists of two or more resistors in series and a source of fixed potential difference.
  13. The Potential Divider - Variable p.d.A potential divider consists of two or more resistors in series and a source of fixed potential difference.
  14. Sensor Circuits - TemperatureA sensor circuit produces an output p.d. that changes as a result of a physical variable such as temperature or light intensity.
  15. Sensor Circuits - LightA light sensor circuit produces an output p.d. that changes as a result of a change in light intensity.

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