GCSE Science - P5

Current
1. The flow of negative electrons around a circuit
2. Cannot flow through an insulator because electrons are not free to move
3. In a current metal conductors are full of charges which are free to move
4. Depends on the Voltage and Resistance
  1. Voltage is measured in volts (V) and is the driving force that that pushed the current around a circuit
  2. Resistance is measure in ohms (Ω) and is caused by components in the circuit (e.g. lamps). It slows down the current.
5. Measured in Amps
6. Power is the rate at which an electrical powers supply transfers energy to an appliance
  1. Measured in Watts (W)
Circuit Components
1. Light Dependant Resistors (LDR) changes its resistance depending on how much light there is
  1. Brightness - resistance falls Darkness - resistance rises
2. A Voltmeter measures the potential difference (voltage). They are always set in parallel
3. A Thermistors resistance changes with the temperature. Hot - resistance drops Cold - resistance rises
  1. Hot - resistance drops Cold - resistance rises
4. A Filament Lamp lights up when resistance is created by electrons colliding with metal ions in the metal coil (or filament)
Transformers
1. Used to "step up" or "step down" the voltage using electromagnetic induction
  1. Electromagnetic Induction is when movement plus magnetism create a current. As the magnet turns, the magnetic field through the coil changes inducing a voltage.
2. Works by;
  1. Changing voltage across primary coil
    1. Which changes the current in the primary coil
      1. Which changes the magnetic field
        Which changes the voltage across the secondary coil
        Which changes the current in the secondary coil
3. Works only on AC Voltages (alternating current)

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GCSE Science - P5

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