– 25 –
Experiment 3
Experiment 1 and Experiment 2 used resistors (carbon film resistors). In Experiment 3, we will
use a light bulb in place of resistance, whose filament acts as the resistance. Wire a diagram
like the one shown below.
• Raising power supply voltage too high makes the light bulb very bright and very hot!
• Do not raise power supply voltage over 4V.
As with the previous experiments, this experiment studies the relationship between voltage and
current.
Gradually raise the power supply voltage, measuring voltage and current on either side of the
light bulb. Raise the power supply voltage from 0V to 2V, in 0.2V increments, recording current
values as you go.
Experiment 3 Results
Analysis – Step 1
Use your graphic calculator to graph the results. In the STAT Mode, input the Voltage data into
List 1, and the Current data into List 2.
Analysis – Step 2
Now it’s time to move on to the next step. Is the graph produced by this Experiment different
from the graphs produced in Experiment 1 and Experiment 2? Write what you observe.
The points in the graphs produced by Experiments 1 and 2 are linear and pass
through the origin, but the Experiment 3 graph is not linear.
A_
V_
Ammeter
Power Supply
Voltmeter
Load
(miniature bulb)
R
[Ω]
Voltage (V) 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
Current (A) 0 0.30 0.42 0.48 0.53 0.57 0.60 0.63 0.66 0.69 0.72
EE-2 Ohm’s Law
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