Electricity

• Circuit symbols


  Used to draw circuits simply
• Power supply (cell)


  • Connected to ammeter (in series) and lamp
• Ammeter


  Measures current, always connected in series
• Voltmeter


  Measures potential difference, always connected in parallel
• Electric current


  Rate of flow of electric charge
• Resistor

  • Exhibits a linear relationship between current and potential difference (ohmic conductor)
• Filament lamp

  • Non-ohmic conductor, resistance increases as it gets hotter
• Diode


  • One-way valve, allows current to flow in only one direction
• Light dependent resistor (LDR)


  • Resistance decreases as light intensity increases
• Thermistor

  • Resistance decreases as temperature increases
• Series circuit


  Components connected one after another, same current in all components
• Parallel circuit


  Separate loops, current splits at junctions, same potential difference across components
• Alternating current (AC)


  Current that changes direction repeatedly, used in household mains supply
• Household mains supply

  • 230V, 50Hz frequency, 3 core cable (live, neutral, earth)
• Transformer

  Allows energy to be transferred efficiently over long distances using the National Grid
• Static electricity

  Caused by transfer of electrons between insulators, can create attractive or repulsive forces
• Electric field


  Region around a charged object where other charges experience a force