Why when using a thermistor, as the temperature increases, the output voltage (p.d) also decreases?

Question

This seems to be rather contradictory..! As an increase in the temperature results in a proportional decrease in resistence, right? Which should mean a higher voltage output value the other side..? (as there would a decreased resistence) Afterall, the same applies for a variable resistor where once the the resistence is increased the output voltage is reduced!!!

Answer 1

V=IxR, reduce R reduces V, not increases it.

Answer 2

A thermistor is usually connected to another resistor to form a voltage divider, or a bridge.  The output voltage depends on where in the circuit the thermistor is connected.  If the thermistor is connected into the ground side of the divider, the voltage would decrease, with an increase in temperature.  If its connected in the +ve side of the divider, the output voltage would rise.

There are also two different types of thermistor,  +ve and -ve coefficient.  One increases its resistance with temperature, the other decreases its resistance.

Answer 3

There are 2 types of thermistor NTC = negative temperature coefficient and PTC = positive temperature coefficient. NTC means that as the temperature increases the resistance decreases. With a PTC as the temperature increases the resistance increases. To test yours why not measure the resistance and then increase the temperature and measure again this will indicate if your thermistor is a PTC or NTC. Check out the website below.

Answer 4

  The current is restricted by the thermistor as the temperature increases.

Answer 5

1, it is usually not a proportional decrease in resistance, but a rapeid one. a small increase in temperature causes a large decrease in resistance.

voltage =current x resistance, the current remains constant, so if the resistance is to decrease, then the current multiplied by the resistance would give a smaller number.

hope that helps! :)