ELECTRICITY - LESSON 3
SIMPLE SERIES AND PARALLEL LIGHT BULB CIRCUITS
JULY 7, 2004 CAL POLY POMONA
OBJECTIVE
The objective of this lesson is to build and explain the operation of simple series and parallel light
bulb circuits.
QUESTIONS AND EXPERIMENTS
1. In the last lesson we built and analyzed circuits with one battery and one light bulb as follows:
Battery
Now suppose we add a second identical light bulb in parallel as follows:
A B
a. Make your own drawing of this circuit.
b. Why do we call this a parallel circuit.
c. Draw a picture to illustrate how the electrons are flowing through the circuit.
2. Complete the following Table of Possibilities for the parallel circuit in Question (1).
Possibility Light Bulb Brightness
1A is brighter than B
3. Suppose one student in your class is absolutely convinced that two light bulbs A and B in
parallel should be just as bright as one light bulb by itself. And another student is absolutely
convinced that the parallel light bulbs should be less bright. How would you settle the matter?
4. Build the parallel circuit in Question (1).
a. How do the brightnesses of the two parallel light bulbs A and B compare with one
another? What do you think is going on? Hint - measure the voltages across each light
bulb.
b. Compare the brightnesses of the light bulbs in your parallel circuit with that in your
circuit from the last Lesson containing just one light bulb. What do you think is going
on? Hint - measure and compare the voltages across the battery and the light bulbs.
c. Is it ever possible for just one light bulb to be ON in a parallel circuit? Explain.
5. Now suppose we again start with our one light bulb circuit from Lesson 2 as follows:
1
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