EXPERIMENT NO. 1

AIM:- To find the activation energy Eg of a Thermistor.

APPARATUS :- Thermistor, Thermometer ( 0 to 100 degree C.),Heating arrangement to heat the thermistor, Rheostat, Voltmeter, Milli-Ammeter, Fixed voltage source.

FORMULA:-Activation energy Eg = 0.396 m eV, where m is the slope of the straight line plot obtained for log10 R and 1/T.

CIRCUIT DIAGRAM:-

PROCEDURE:- Make the connections as shown in the circuit diagram. Heat the water in the beaker, so that the thermometer in the beaker should show the temperature of 75 degees C. Then the heating of water is stopped. After some time the thermometer shows the steady temperature.The applied voltage is suitably selected by sliding the slider on rheostat. Note down the voltage and current. Now the voltage across the thermistor should be kept constant throughout the experiment.

As the thermistor cools down, current readings at different temperatures at intervals of 5 degrss C are noted down and entered in observation table.

OBSERVATIONS:-

Sr.
No.

Temperature (Degrees C.)

Voltage (Volts)

Current (mA)

Resistance (ohms)

Temperature (Degrees K)

103 / T

Log10 R

1
2
3
4
5
6
7
8
9

80
75
70
65
60
55
50
45
40

            

GRAPH:-

Plot a graph of log10 R against 1/T. Slope of the curve is determined.

CALCULATIONS:-

Eg = slope x 0.396 eV.

RESULT:-

The activation energy of given thermistor is found to be      eV.

PRECAUTIONS:-

  1. The temperature of the thermistor should not go beyond 80 degrees C.
  2. The thermistor should be very close to mercury bulb of thermometer.