As the temperature of an NTC thermistor increases, how does the resistance change?

NTC means negative temperature coefficient. This means resistance decreases as you increase temperature. Unless clearly told otherwise assume a thermistor's resistance does this.

Here are some slides with a little more information:

In an NTC thermistor, as the temperature increases the resistance decreases. This is because more electrons become available for conduction.

The resistance decreases as the temperature increases.

Hi Kris! I'm a Physics Professor and personally love this topic out of them all (I could go on for hours!). So, to get started, a thermistor is a semi-conductor which means it's not quite a full conductor but not quite a full insulator. I guess you could say it's BANG in the middle! Now onto the good stuff baby! As a thermistor's temperature increases, it's resistance decreases as there's more cheeky little electrons! PEACE!