Electricity

• What is the function of an ammeter?

  To measure current in a circuit
• How does a light-dependent resistor (LDR) behave in bright light?

  It has low resistance, allowing lots of current to flow
• What happens to the resistance of an LDR in darkness?

  The resistance is high, so hardly any current flows
• What are some applications of light-dependent resistors (LDRs)?

  • Automatic nightlights
  • Burglar alarms
• How does an LDR activate a burglar alarm when a light is switched on?

  The resistance drops, allowing more current to flow, which powers the alarm
• What is the behavior of a thermistor when the temperature is high?

  The resistance is low
• What happens to the resistance of a thermistor when the temperature is cold?

  The resistance is high
• What is a variable resistor?

  • A resistor that allows easy adjustment of its resistance
• What is a fixed resistor?

  • A resistor that cannot vary the amount of resistance it provides
• What is the purpose of the National Grid?

  • Links power stations to homes, offices, and more
• What do transformers do in the National Grid?

  They change the potential difference of an alternating current
• At what potential difference do power stations generate electricity?

  25,000 V
• What do step-up transformers do in the National Grid?

  They increase the potential difference to 400,000 V
• What do step-down transformers do?

  They decrease the potential difference to make it safe for use in homes
• What potential difference do homes and offices use electricity supplied at?

  230 V
• What are the three types of wires in a plug and their functions?

  • Earth wire (yellow and green): safety wire, carries current when there's a fault
  • Neutral wire (blue): completes the circuit
  • Live wire (brown): dangerous wire, carries 230 V
• What type of current does a cell or battery provide?

  Direct current
• How does direct current flow?

  It flows in one direction
• What type of current does mains electricity provide?

  Alternating current
• How does alternating current behave?

  It repeatedly reverses direction
• What produces alternating current?

  Alternating potential difference
• What happens to the overall circuit when one component in a parallel circuit fails?

  The overall circuit will still work.
• Why do parallel circuits continue to function when one component fails?

  Because current can still flow through the other loops.