Transcript ldr / thermistor

What we will do today:
• Draw and identify the symbols for
LDR’s and Thermistors.
• Carry out experiments to investigate
LDR’s and Thermistors.
Thermistor
• A thermistor is an input device that has a
resistance that changes as its temperature
changes.
• It has the symbol:
• We can investigate how the resistance of a
thermistor changes as we increase the
temperature on it.
Thermistor
Temperature of
water
Cold water
Hot water
Resistance of
thermistor ()
Conclusion
• For a thermistor, as the temperature
increases, the resistance decreases.
• Thermistor: T  R  (therefore I )
• TURD
Light Dependent Resistor
(LDR)
• An LDR is an input device which has a
resistance that changes as the intensity of
light falling on it changes.
• It has the following symbol:
• We can investigate how the resistance of
an LDR changes as we increase the light
intensity on it.
LDR
Light level
Completely dark
Dim light
Bright light
Resistance of
LDR ()
Conclusion
• For an LDR, as the light intensity
increases, the resistance decreases.
• LDR: Light  R  (therefore I )
• LURD
2004 Qu: 14
2005