Electricity

• current —> rate or flow of charge
• ammeter —> placed in series

  voltmeter —> placed in parallel
• What I-V characteristic graph is this?

  Ohmic Conductor

  
• What I-V characteristic graph is this?

  Filament Lamp

  
• What I-V characteristic graph is this?

  Diode

  
• I-V characteristic —> a graph that shows the current flowing though a component that changes as the P.D is increased
• LDR —> in bright light, the resistance falls; in darkness, resistance is highest

  Applications include automatic night lights, outdoor lighting and burglar detectors
• Thermistor —> temperature dependent resistor

  hot conditions = resistance drops

  cool conditions = resistance increase

  Applications include temperature detectors (like thermostats and car engine temperature sensors)
• Sensing Circuits —> can be used to turn on/ increase power depending on conditions

  The fixed resistor and the fan will always have the same P.D. (because they’re connected in parallel
• Series Circuits —> components are connected in a line, current is the same everywhere.

  However, this means of one component is removed/ disconnected the whole circuit breaks

  The total pd and resistance of the supply is shared between various components (so V total = V1 + V2… and R total = R1 + R2)
• diodes --> don't allow for backflow of current as they have very high resistance in the reverse direction
• the UK's mains electricity supply is alternating current
• In a plug:

  -blue wire = neutral wire

  -yellow and blue wire = earth wire

  -brown wire = live wire
• neutral wire --> completes the circuit with the live wire, meaning electricity can flow. It is around 0 V
• Even if a plug socket is turned off there is still a danger of an electric shock.

  A current isn’t flowing but there’s still a potential difference between you and the live wire. If you made contact with the live wire, your body would provide a link between the supply and the earth, so a current would flow through you.