topic 10 - electricity and circuits

• What does AC stand for?

  Alternating Current
• What characterizes Alternating Current (AC)?

  It constantly changes between negative and positive
• Is mains electricity an AC or DC supply?

  AC supply
• What does DC stand for?

  Direct Current
• What is the characteristic of Direct Current (DC)?

  It takes a constant value
• What is the frequency of the UK mains electricity supply?

  50 Hz
• What is the voltage of the UK mains electricity supply?

  230V
• What does the power rating of an appliance indicate?

  Energy converted per second
• What type of current do batteries supply?

  Direct current
• What does frequency refer to in an AC supply?

  Rate at which AC current changes
• What color is the live wire?

  Brown
• What wires does a typical appliance have?

  • Live wire
  • Neutral wire
  • Earth wire
• What color is the earth wire?

  Green and yellow (striped)
• What potential is the neutral wire at?

  0 Volts
• When does the Earth wire carry current?

  • No current flows under normal circumstances
  • Current flows during a fault in the appliance
• What color is the neutral wire?

  Blue
• What is the purpose of the neutral wire?

  To complete the circuit back to mains
• How does a fuse wire protect an appliance?

  It melts and breaks the circuit
• Where is the Earth wire connected in metal appliances?

  • Connected to the metal casing
  • Prevents electrocution if live wire touches casing
• What is the potential difference between the live and earth wires?

  230 Volts
• Why is it important to connect a fuse to the live wire?

  It breaks the circuit to stop current
• What factors affect energy transferred when charge flows?

  • Current
  • Potential difference
  • Resistance
• What is the equation linking energy, current, and potential difference?

  Energy = Current x Potential Difference x Time
• Why is a connection between earth and live wires dangerous?

  It can cause a current surge
• What is the equation relating potential difference to charge?

  Potential Difference = Charge / Energy
• How do low resistance wires reduce unwanted energy transfers?

  They minimize heat loss during current flow
• Why does a resistor heat up when current flows through it?

  Electrons collide with metal ions
• How is potential difference defined in terms of charge?

  Potential difference is energy per unit charge
• What are some disadvantages of the heating effect?

  • Energy loss as heat
  • Potential damage to components
  • Reduced efficiency
• What is the definition of power?

  Energy transferred per second
• What is another term for energy transferred per second?

  Power
• What are some advantages of the heating effect?

  • Useful in heating appliances
  • Enables temperature control
  • Can be used for cooking
• What is the equation linking power and potential difference?

  Power = Voltage x Current
• What is the equation linking power and energy?

  Power = Energy / Time
• What is the equation to work out power without potential difference?

  Power = Current^2 x Resistance
• What are the units of power?

  Watts (W)
• How can the current in a circuit be varied?

  • Using a variable resistor
  • Adjusting resistance in the circuit
• How does resistance affect current in a circuit?

  Increased resistance decreases current flow
• What are the equations linking power with resistance?

  Power = Current^2 x Resistance
• How is total resistance affected by two resistors in series?

  Total resistance increases; sum of resistors