GCSE Physics (AQA)

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Light-Dependent Resistors

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Electricity Current, potential difference and resistance

Light-Dependent Resistors

3:37 Resistance of Circuit Components
Spec 4.2.1.1 4.2.1.4
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  • A light dependent resistor (LDR) changes its resistance based on light intensity.
  • The wavy conductor on top acts as a sensor reacting to light.
  • Resistance changes due to the release of more charge carriers.
  • The circuit symbol for an LDR is a rectangle in a circle with two arrows indicating light reaction.
  • LDR is abbreviated from light dependent resistor.
  • LDR resistance decreases as light intensity increases.
  • On an IV graph, potential difference is on the horizontal axis and current on the vertical axis.
  • In dim conditions, the LDR shows a straight line through the origin, indicating constant resistance.
  • In bright conditions, the graph is steeper, indicating lower resistance.
  • The gradient of an IV graph indicates the resistance of the component.
  • LDRs are used in circuits that need to react to light intensity changes, such as security lights and smartphone screens.
  • LDRs help measure brightness and adjust resistance and current accordingly.
  • For exams, understanding the usefulness of LDRs in devices is important, though recalling specific examples is not necessary.

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