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LDR response to light

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Objective

Use a light-dependent resistor in a divider: more light → lower resistance → higher output voltage.

Procedure

  1. Change the LDR 'lux' parameter (1, 10, 100, 1000) in the Inspector and run each time.

Theory

R(LDR) falls roughly as lux^−γ. In a divider with a 10 kΩ resistor the output rises from a few tenths of a volt in the dark to several volts in bright light.

Questions to answer

  1. Why is an LDR slow compared with a photodiode?

Components used

Battery / DC source, LDR GL5528, Resistor 220 ohm 1/4W

About the model

Ideal wires; component models as listed in the catalogue (no parasitics, no temperature drift). Built without a breadboard so the schematic stays readable.

Open this experiment in the circuit simulator

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