BRAINCAKE

Electricity and circuits

Edexcel GCSE PhysicsTopic 10 of 1542 lessons

Revision notes for Electricity and circuits in Edexcel Physics (1PH0). Every lesson in BrainCake comes with R.E.C.I.P.E. recall steps, a quick check and spaced reviews.

  1. Structure of the atomEvery atom has a tiny nucleus at its centre.
  2. Circuit diagrams and symbolsA circuit diagram uses standard symbols so that anyone can read it.
  3. Series and parallel circuitsIn a series circuit all the components are joined end to end in one single loop, so there is only one path for the current.
  4. Using a voltmeterA voltmeter measures the potential difference, also called the voltage, across a component.
  5. Potential difference and the voltIn a circuit, charge flows round the loop and carries energy with it.
  6. Energy, charge and potential differenceThe energy transferred depends on how much charge moves and on the potential difference it moves through.
  7. Measuring current with an ammeterAn ammeter is the meter used to measure the current in a component.
  8. Current as a flow of chargeAn electric current is the rate of flow of electric charge.
  9. Charge, current and timeThe charge that flows past a point depends on the current and on how long it flows.
  10. Current in a closed circuitFor there to be a current in a circuit, two things are needed.
  11. Current at a junctionA junction is a point where wires join and the current can split or combine.
  12. Resistance and variable resistorsResistance is how much a component opposes the flow of current.
  13. Potential difference, current and resistanceThe resistance of a component is how strongly it opposes the flow of current.
  14. Resistors in series and in parallelIn a series circuit the components are connected one after another in a single loop, so the charge has to pass through every resistor in turn.
  15. Calculations for series circuitsIn a series circuit there is only one loop, so three rules apply.
  16. Designing series circuits for testing and measuringA series test circuit is built from a power supply, a switch, connecting wires, the component being tested and measuring instruments.
  17. Core practical: resistor and filament lampThis practical investigates how the current through a component depends on the potential difference across it, for a fixed resistor and then for a…
  18. Current and potential difference graphsA graph of current against potential difference shows how a component behaves, and its shape tells you how its resistance changes.
  19. Light-dependent resistors (LDRs)A light-dependent resistor (LDR) is a component whose resistance changes with the light falling on it.
  20. ThermistorsA thermistor is a resistor whose resistance depends on its temperature.
  21. Investigating resistance in devicesTo explore how the resistance of a component changes, build a test circuit.
  22. The heating effect of a currentWhen there is an electric current in a resistor, energy is transferred electrically from the power supply to the resistor.
  23. Energy dissipated by resistanceCharges moving through a circuit do work against the resistance of the components and wires.
  24. Why resistors heat upA metal wire or resistor contains a lattice of positive ions, held in fixed positions, with free electrons that can move through it.
  25. Reducing unwanted energy transfer in low resistance wiresWhen there is a current in a wire, electrons collide with the ions in the lattice of the metal.
  26. Advantages and disadvantages of the heating effect of a currentWhen there is a current in a resistor, electrical energy is transferred as thermal energy.
  27. Energy transferred: E = I × V × tWhen a current is in a component, the energy transferred depends on three things: the current, the potential difference across the component, and…
  28. Power as energy transferred per secondPower is the rate at which energy is transferred, which means the energy transferred per second.
  29. Power equation: P = E ÷ tPower is the energy transferred each second, so we calculate it by dividing the energy transferred by the time taken: power = energy transferred ÷…
  30. Power, potential difference and currentThe potential difference across a component is the energy transferred for each coulomb of charge that passes through it.
  31. Electrical power equationsElectrical power is the energy transferred each second, and it is measured in watt (W).
  32. Energy transfers in domestic devicesDomestic devices transfer energy from a supply to the stores where it is useful.
  33. Direct and alternating voltageA direct voltage always pushes charge in the same direction.
  34. Direct currentDirect current (d.c.) is the movement of charge in one direction only.
  35. Alternating currentIn alternating current (a.c.) the movement of charge changes direction.
  36. UK domestic mains supplyThe domestic supply in the UK is alternating current (a.c.).
  37. Live and neutral mains wiresThe mains supply in the UK is alternating current.
  38. Earth wires, fuses and circuit breakersMany appliances have a metal case.
  39. Switches and fuses in the live wireIn a domestic circuit, switches and fuses are connected in the live wire.
  40. Potential differences of the mains wiresThe three wires in a mains supply are at different potentials.
  41. Dangers of connecting live to earthThe earth wire gives current an easy path to earth, because it has a very low resistance.
  42. Power ratings and energy changesThe power rating of an appliance tells you how much energy it transfers each second when it is working normally.

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