GCSE Combined Science (AQA)

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Resistance

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Electricity Current, potential difference and resistance

Resistance

4:15 Potential Difference and Resistance
Spec 4.2.1.1 4.2.1.3
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  • Resistance measures how much a component opposes current flow.
  • Current consists of delocalized electrons slowed by collisions with positive ions.
  • Resistance is measured in ohms, represented by the Greek letter omega.
  • Greater resistance means more charge carriers are slowed, opposing current.
  • All components have some resistance; some are designed specifically for it.
  • Resistors are components designed to reduce currents deliberately.
  • Fixed resistors have a set resistance value, which can change if overheated.
  • Fixed resistors have colored stripes indicating resistance value.
  • Circuit symbol for a fixed resistor is a rectangle.
  • Resistors reduce current in circuits to prevent overheating or breaking components.
  • Resistors can adjust current division in branching circuits or as conditions change.
  • Variable resistors can change resistance, affecting current flow.
  • Variable resistors have a high resistance conductor adjusted by a dial or slider.
  • Circuit symbol for a variable resistor includes a diagonal arrow through it.
  • Variable resistors adjust resistance and current in circuits dynamically.
  • Used in circuits like dimmer switches to change lamp brightness without disconnecting components.

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