resistors

• • the resistance remains constant in some resistors
  • the resistance can change in some resistors as the current changes
• • the current through an ohmic conductor at a constant temperature is directly proportional to the difference across the resistor
  • the resistance remains constant as the current changes
  • graph = straight line
• filament lamp:

  • as the current increases, the temperature increases so the resistance increases
  • graph = s curve through 0
• diode:

  • current through a diode flows in one direction
  • the diode had very high resistance in reverse direction
  • graph = reverse L
• • the resistance of an LDR decreases as light intensity increases
  • the resistance of an LDR increases as light intensity decreases -——- LDRS are needed in circuits as switching on lights when it is dark is needed
• • the resistance of a thermistor decreases as temperature increases
  • the resistance of a thermistor increases as temperature decreases
  • thermistors are needed in circuits because they make required thermostats