Aim: To test if a light globe is an Ohmic or Nonohmic resistor.
Apparatus: Light Globe
Resistor
Power Supply
Ammeter
Voltmeter
Connecting Wires
Method:
1) Set up apparatus as shown in diagram 1.
2) Record the reading on both the Ammeter and Voltmeter then turn on the power supply and record the readings again.
3) Increase the volts on the power supply and record the reading.
4) Repeat step 3 four more times
5) Record results in a table
Results:
Voltage (V) Current x103 (A) R=V/I
Ω
Resistor 2.00 0.42 4761.9
4700±5% 4.00 0.85 4705.8
6.00
8.00
10.00
12.00 1.28
1.67
2.14
2.55 4687.5
4790.4
4672.8
4705.8
Light Globe 2.00 28.3 70.6
4.00 46.7 85.6
6.00
8.00
10.00
12.00 61.4
73.5
84.6
92.4 97.7
108.8
118.2
129.9
Results:
Question: The difference that you would expect to see in a Ohmic and a Nonohmic graph is that a Ohmic graph would be a straight line stating that it s constant and a Nonohmic would show a curve showing that it is not constant in current against voltage.
Three errors that could have affected this experiment could include the condition of the equipment could lead to the equipment not reading properly and that would affect the results. Another could be the readings taken during the experiment so equipment used does not show an exact reading eg. an analog display and that relies on the person’s ability to record the readings exactly. Lastly when changing the connection on the various apparatus a lead or clip might have loosened and changed the results.
Conclusion: By doing this experiment it has shown that a light globe is a Nonohmic resistor in that the when changing the voltage running through the circuit the resistance in the light globe changed. Also by plotting the recorded information on a graph the graph with the light globe was curved unlike the graph of the Ohmic resistor stating their different resistors.