P2

• What does amount of energy an appliance transfers rely on?

  Time and power rating
• How do appliances transfer energy?

  Electrically - through batteries or ac mains
• What is charge measured in?

  coulombs
• What does power rating show?

  How much energy is needed for an appliance to work
• What is the national grid?

  Network of cables and transformers connecting power stations to homes and businesses
• Why does the national grid use high potential difference and low current

  High currents lead to a significant amount of energy transfer as heat- high potential difference allows for a low current - increased efficiency as energy loss is reduced
• What do transformers do?

  Change the potential difference - makes it more efficent

  • step up - increase potential difference and decrease current
  • step down - decrease potential difference and increase current
• What is the potential difference of mains electricity?

  230v
• What is the frequency of mains electricity?

  50Hz
• What is current measured in?

  Amperes - (A)
• What is resistance measured in?

  Ohms (weird greek symbol)
• What is direct current?

  Current flowing in one direction
• What is alternating current?

  Current that changes direction regularly
• What colour is the Earth wire?

  Yellow and green
• What colour is the neutral wire?

  Blue
• What colour is the live wire?

  Brown
• What does the live wire do?

  Carries potential difference - connected to fuse
• What does the neutral wire do?

  Completes the circuit - 0v
• What does the Earth wire do?

  Prevents the appliance from becoming live - 0v -only works if there's a fault
• Why is plastic used in casing?

  Good insulator
• What does the fuse do?


  if the appliance short circuits the fuse melts, breaking the circuit
• What is current?


  Flow of electric charge
• What does current do in a single closed loop?

  remain the same value throughout
• What is current measured in?

  Amperes
• Which side of the cell does the current flow from?

  Positive (longer line)
• What is potential difference?

  Measure of energy per unit of charge transferred between two points in a circuit
• What does resistance do?

  Slows the flow of current - higher the resistance, lower the current
• What is ohms law?

  Current is directly proportional to potential difference
• What is a series circuit?

  A circuit where all components are in 1 loop
• What is a parallel circuit?

  Components are in multiple loops
• How does current flow in a series circuit?

  Same through each components
• how does current flow in a parallel circuit?

  Sum of current through all the components
• what is potential difference in a series circuit?

  Shared between components
• What is potential difference in a parallel circuit?

  Same across each component
• How does increasing number of resistors impact current in a series circuit?

  Increases total resistance
• What is resistance in a parallel circuit? why?

  Less that the smallest individual resistance

  each resistor added adds a different path along which current can flow - larger total current that can flow so less resistance
• Why is the Earth wire good?

  Provides a low resistance path to the Earth, when this happens current flows into the ground, the fuse may melt in this case as there is a surge in electricity, breaking the circuit and making the appliance safe to touch
• What is a closed switch

  completes the circuit and allows current to flow
• What is an open switch

  Makes the circuit incomplete so current cannot flow
• What is a cell?


  Single battery that provides potential difference needed for current to flow