Resistors (AQA GCSE Physics): Revision Note

Constant & Variable Resistance

• Resistors come in two types:

  • Fixed resistors

  • Variable resistors

• Fixed resistors have a resistance that remains constant

• Variable resistors can change the resistance of the circuit

  • Increasing the resistance of a variable resistor in a series circuit decreases the current

  • The potential difference across the other components (such as a lamp) also decreases

  • The total resistance of the circuit increases

• For fixed and variable resistors, once the resistance is set, it stays at this value as the current changes, as long as the temperature stays constant

• However, the resistance of components such as lamps, diodes (including LEDs), thermistors and LDRs (light dependent resistors) changes with the current through the component

Fixed and variable resistor circuit symbols