Ohm's Law

A thermistor is an electrical device that changes electrical properties with changes in temperature in a predictable manner. It is used to measure extreme temperatures where a conventional thermometer might freeze or break. It is also used to control electrical devices that are dependent on temperature control (such as an air conditioner.)

a. In the following chart, the temperature in degrees Celsius is given in relation to the variable R, which is measured in 1000's of Ohms. Have JMP fit a line to this data with T as the x-variable and R as the y-variable.

b. Ohm's Law is an empirical relationship relating electric potential (V) to current (I). The proportionality constant (R) is called the resistance. This formula is

V = RI.

If the voltage in a circuit containing a thermistor is 20 volts and the current in the circuit is 0.0005 Amps, find the temperature of the thermistor. You will need to use the equation that you found in part a) as well as Ohm's Law to find the temperature.

c. If the voltage is fixed at 5 volts, combine the equation you got in part a with Ohm's Law to write an equation containing only the variables T and I. Solve this equation for T. Graph this equation on graph paper with I as the independent variable and T as the dependent variable.