A thermistor is made from a semiconducting material, usually a mixture of metal oxides.A thermistor at constant temperature gives an IV graph that is a straight line.The higher the temperature, the steeper the gradient of the line.This is because resistance decreases with an increase in temperature.The I-V graph for a thermistor curves upwards, indicating decreasing resistance with increased current due to temperature rise.The same result is obtained for a light dependent resistor.gradient = 1/resistance 