LDRs and thermistors (AQA GCSE Physics Combined Science): Flashcards
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14 cards from this deck
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Practise the cards
14 cards from this deck
LDR stands for
LDR stands for
Light-Dependent Resistor
Thermistor stands for
Thermistor stands for
Thermal resistor
LDR resistance in the dark
LDR resistance in the dark
Very high (several megaohms)
LDR resistance in bright light
LDR resistance in bright light
Much lower (few hundred ohms)
LDR: brightness up → resistance ?
LDR: brightness up → resistance ?
Down
Thermistor: temperature up → resistance ?
Thermistor: temperature up → resistance ?
Down
Three uses of LDRs
Three uses of LDRs
Street lights, security lights, automatic car headlights
Three uses of thermistors
Three uses of thermistors
Thermostats, temperature alarms, electronic thermometers
Current through LDR in bright light
Current through LDR in bright light
More current flows (resistance is low)
Current through LDR in darkness
Current through LDR in darkness
Less current flows (resistance is high)
Current through thermistor at high temp
Current through thermistor at high temp
More current flows (resistance is low)
Most common thermistor type
Most common thermistor type
NTC (Negative Temperature Coefficient)
How LDRs & thermistors change resistance
How LDRs & thermistors change resistance
Smoothly and continuously, not on/off
Thermistor resistance when cold
Thermistor resistance when cold
High