Circuits

• Positive and negative charges

  Positive and negative charges
• Charges that attract


  • Positive and negative
• Charges that repel


  • Negative and negative
  • Positive and positive
• Current


  The amount of charge flowing per second
• Switch


  Opens and closes a gap in the circuit
• Unit of current


  Amps (A)
• Battery


  Pushes charge around a circuit
• Series circuit


  • Diagram
• Parallel circuit


  • Diagram
• Current in series circuit

  • It is the same everywhere
• Current in parallel circuit

  • It divides up between the branches
• Potential difference in series circuit


  • The potential difference across the components adds up to the potential difference of the battery
• Potential difference in parallel circuit


  • The potential difference across each component is the same as the potential difference across the battery
• Resistance


  How easy or difficult it is for electrons to pass through a circuit
• Unit of resistance


  Ohms (Ω)
• Factors affecting resistance

  • The diameter of wire
  • The length of wire
  • The temperature of the conductor
• Fixed vs variable resistance


  A fixed resistor always has the same resistance whereas in a variable resistor the resistance can be changed
• Fuse


  A safety device that protects an electric circuit from overheating
• Standard fuse ratings


  • 3A
  • 5A
  • 10A
  • 13A
• Wires in a plug


  • Live
  • Earth
  • Neutral
• Function of live wire

  Completes the circuit and powers the appliance
• Function of earth wire


  Safety wire
• Function of neutral wire


  Completes the circuit and powers the appliance
• Efficiency


  How much useful energy is transferred from the total electrical energy input
• Sankey diagram for a lightbulb


  • 1001 energy supplied, 101 useful energy, 901 wasted energy
• Calculating efficiency as a percentage


  Efficiency = useful energy out / total energy in