Assessment week 2

• DC = Direct current
• AC = Alternating Current
• Charge is a property of an electron that is measured in coulombs (C)
• Current is the rate of flow of charge through a circuit, measured in amps (A)
• Potential Difference is the energy difference per unit charge between two points in a circuit measured in volts (V)
• Resistance is the potential difference to produce a current of 1 Amp measured in ohms
• A thermistor has a lower resistance when it is hot and a higher resistance when it is cold.
• A light dependant resistor has a lower resistance in a brighter light.
• This is a diode

  
• This is a Filament lamp

  
• The live wire carries the alternating potential difference from the power supply.
• The neutral wire is the wire that completes the circuit so the potential difference is always close to 0V.
• No current flows in the earth wire unless there is a fault.
• The neutral wire is blue.
• The earth wire is green and yellow.
• The live wire is brown.
• Wire

  • Current is proportional to potential difference
  • Resistance is constant
• Filament lamp

  • Current increases with increasing potential difference but not proportional
  • Resistance increases
• Diode

  • When potential difference is applied negatively no current flows the resistance is very high
  • When potential difference is applied positively below a threshold there is no current but then current increases rapidly the resistance is low
• Direct current - there is a constant potential difference in one direction and the current is constant (from positive to negative)
• Alternating current - there is a changing potential difference from positive to negative. The current changes direction.