Paper 1

• electrical conductor


  allows an electric current to pass through material easily
• energy equation (1)


  power x time
• national grid:


  distributes electricity across the country, connects power stations to homes, workplaces and public buildings around the country
• transformer


  an electrical device that increases or decreases the potential difference (voltage) of a current
• transmission lines:


  thick cables to carry electricity long distances through the national grid
• increasing voltage


  decreases current
• decreasing voltage:


  increasing current
• step up transformer


  a transformer that increases the voltage of ac supply
• power equation (2)


  potentital difference x current
• power equation (3)


  current squared x resistance
• power unit


  watts
• current unit


  amps
• resistance unit


  ohms
• energy unit


  joules
• time unit

  seconds
• What is the main characteristic of parallel circuits?


  They contain more than one loop
• How does the configuration of circuits affect measurements of current, voltage, and resistance?


  The configuration completely changes how we measure these quantities
• How is the potential difference of a battery distributed in a series circuit?


  It is shared across all components
• How is current measured in a circuit?


  Using an ammeter
• Why can ammeters be ignored in calculations?


  They generally have very tiny resistances
• How can you find the voltage across a component without calculations?


  By using a voltmeter connected in parallel across the component
• Electrons are negatively charged particles and they transfer energy through wires as electricity.
• charge = current × time
• charge (Q) is measured in coulombs (C)
• current (I) is measured in amps (A)
• time (t) is measured in seconds (s)
• Potential difference equation (2)


  Energy/charge
• What happens when a charge moves through a potential difference


  Electrical work is done and energy Electrical work is done and energy
• What is the focus of the investigation described in the study material?


  The resistance of a wire and how it changes with the length of the wire
• Why is copper wire not used in this experiment?


  Because its resistance is too small to measure easily
• What type of wire is used in this investigation?

  Nichrome wire
• How long should the nichrome wire be for the experiment?


  A meter length
• What is the purpose of the voltmeter in the circuit?


  To measure the potential difference across the wire
• What components are included in the series circuit for this experiment?


  Battery, ammeter, and resistance wire
• Why is a double length cable used in the circuit setup?


  To ensure plenty of reach for connecting the circuit
• How does the resistance of a short piece of wire affect the experiment?


  It can cause the current to get too large, leading to heating and changing resistance
• How is resistance calculated for each length of wire?


  By dividing the potential difference by the current
• What law is used to calculate the resistance in this experiment?

  Ohm's law
• What steps should be taken after completing the measurements in the experiment?

  • Disconnect the power supply to stop current flow
  • Disconnect the circuit between readings to prevent overheating
  • Ensure the circuit is connected for the shortest time possible
• How should the graph of resistance against length be plotted?


  • Resistance on the y-axis
  • Length on the x-axis
  • Draw a line of best fit through the points
  • Ideally, it should be a straight line with a positive gradient through the origin