2.1.4 Resistors

• For some resistors, the value of R remains constant as the current changes.
• The current through an ohmic conductor (at a constant temperature) is directly proportional to the potential difference across the resistor, meaning the resistance remains constant as the current changes.
• The resistance of components like lamps, diodes, thermistors, and LDRs is not constant; it changes with the current through the component.
• The resistance of a filament lamp increases as the temperature of the filament increases.
• The current through a diode flows in one direction only, and the diode has very high resistance in the reverse direction.
• The resistance of a thermistor decreases as the temperature increases.
• Thermistors have applications in circuits, for example, in a thermostat.
• The resistance of an LDR decreases as light intensity increases.
• What is this a graph for?

  The resistance of a filament lamp.

  
• What is this a graph for?

  The current and potential difference through a diode.

  
• Adding identical resistors to a series circuit what?

  Increases the total resistance.
• Adding identical resistors to a parallel circuit what?

  Decreases the total resistance.
• What is this a graph for?

  The resistance of an ohmic conductor.

  
• What is one application of LDRs in circuits?

  Switching lights on when it gets dark.