topic 10 electricity

• What is electric current defined as?

  The rate of flow of charge
• What constitutes current in metals?

  Flow of electrons
• What happens when a closed circuit includes a source of potential difference?

  There will be a current in the circuit
• What is conserved at a junction in a circuit?

  Current
• How does changing resistance in a circuit affect current?

  It changes the current
• How can you change the current of a supply in a circuit?

  Use a variable resistor
• What happens when resistors are added in series?

  • Total resistance increases
  • Resistors share total potential difference (pd)
  • Current through each resistor decreases
  • Total current in circuit is reduced
• What is the effect of adding resistors in parallel?

  • Total resistance decreases
  • Total resistance is less than the smallest resistor
  • Same pd across each resistor
  • Increases total current that can flow
• What type of graph do filament lamps produce?

  Non-linear graphs
• How does increasing current affect a filament lamp?

  Increases temperature and resistance
• What is a diode's function in a circuit?

  Allows current to flow in one direction
• How do resistors and wires behave in relation to current and potential difference?

  Current is directly proportional to pd
• What does LDR stand for?

  Light dependent resistor
• How does resistance change in an LDR in bright light?

  Resistance falls
• What is the behavior of a thermistor as temperature increases?

  Resistance decreases
• What happens to current through a thermistor as temperature increases?

  Current increases as resistance decreases
• What occurs when there is an electric current in a resistor?

  Energy transfer heats the resistor
• What happens to electrical energy when it does work against resistance?

  It is dissipated as thermal energy
• Why does a resistor heat up when current flows through it?

  Electrons collide with ions in the lattice
• How does the vibration of ions in a resistor affect current?

  Increases collisions, decreasing current
• What is the effect of low resistance wires on energy dissipation?

  Reduces energy dissipated to thermal stores
• What are the advantages and disadvantages of fuses?

  Advantages:

  • Protect circuits by melting if current is too high
  • Used in heating appliances like toasters

  
  

  Disadvantages:

  • Reduces efficiency
  • More energy is lost as thermal energy
• How is power defined in electrical terms?

  Energy transferred per second
• What does power transferred depend on?

  Potential difference and current
• What is the formula for power in terms of current and potential difference?

  Power = current x potential difference
• What is the formula for power in terms of current and resistance?

  Power = current$^2$ x resistance
• What does a power rating indicate for appliances?

  Maximum safe power they operate at
• How does power rating help customers?

  Helps choose between appliance models
• What does a lower power rating imply about an appliance?

  Uses less electricity and cheaper to run
• Does a higher power rating guarantee more useful energy transfer?

  No, it may be less efficient