P3.2.5 - LDRs and thermistors Flashcards
What are thermistors?
They are components whose resistance depends upon temperature
The higher the temperature in a thermistor…
the lower the resistance
As you heat a thermistor/semi-conductor…
- ions vibrate faster
- more electrons are liberated from the atoms of semi-conductor
At high temperatures in a thermistor…
the current is high so the resistance of the thermistor is low
At low temperatures in a thermistor…
the current is low so the resistance of the thermistor is high
What are LDRs?
They are components whose resistance depends upon light intensity
As the light intensity in an LDR increases…
the resistance decreases
What are LDRs and thermistors made of?
Semi-conducting material
As you give an LDR/semi-conductor more light…
- ions vibrates faster
- more electrons are liberated from atoms of the semi-conductor
Why do the graphs of resistance against temperature and light intensity eventually level off?
After a certain amount of heat or light energy, all the electrons would have been liberated so resistance will no longer change with increasing temperature
