Activity for
Framework Physics 10
To investigate the relationship between current (I),
potential difference (V) and resistance (R) in a simple
circuit using a resistor
This activity relates to OP49 and OP50 of the Junior Certificate Science Syllabus.
Apparatus
Vernier LabPro interface or LabQuest, Laptop, Current Probe, Voltage Probe, Logger Pro, a variable d.c.
power supply, a 10 ohm resistor, and a filament light bulb.
Diagram
Method
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Connect the Current Probe to Channel 1 and the Voltage Probe to Channel 2 of LabPro.
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Open the file “25 Ohms Law” in the Physics with Computers/Vernier folder. A graph showing
axes labeled of potential vs. current will be displayed. The LabQuest/laptop displays the potential
difference and current readings.
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With the power supply turned off, connect the power supply, 10 ohm resistor, wires, and clips as
shown in the diagram above.
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Click ZERO. A dialog box will appear. Click OK to zero both sensors. This sets the zero for both
probes with no current flowing and with no voltage applied.
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Make sure the power supply is set to 0 V. Click COLLECT to begin data collection. Monitor the
voltage and current. When the readings are stable click KEEP.
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Increase the voltage on the power supply to approximately 0.5 V. When the readings are stable
click KEEP.
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Continue to Increase the voltage by about 0.5 V. When the readings are stable click KEEP. Repeat
this process until you reach a voltage of about 5.0 V.
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Click STOP.
Activity for Framework Physics 10
Results
Conclusion
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The straight line graph through the origin shows that current is proportional to voltage.
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The resistance can be found by dividing the potential difference by the appropriate current for
each set of readings and finding an average.
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The resistance can also be found by finding the slope of the graph.
Extension
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Replace the resistor in the circuit with a filament light bulb. Repeat the steps outlined above
increasing the voltage up to 5.0 V again. Comment on the shape of the graph for the filament
light bulb. Why is it different to the graph obtained for the 10 ohm resistor?
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