PHYSICS 1B WEEK #6
CIRCUITS WITH BATTERIES AND BULBS
Rev 1
INTRODUCTION: This lab relates to material in Hecht 2nd ed. Chapters 17 and 18. In
this lab you will explore the concept of the circuit using batteries, wires, and one light
bulb. It is a good idea to read all the steps in each part before you start. Note that there is
one set-up of Part 1 and your group will need to cycle through that station at some point
during the lab. Pages 1 and 2 are what we expect you to complete. The extra material in
the Appendix (pages 3 to end) is optional. You may try out these circuits if you have
time.
Material in this lab has been adapted from McDermott Tutorials in Introductory Physics.
Pre-Lab Homework
Directions: These pre-lab homework problems are to be done before you get to lab.
They are predictions, your hypothesis of what you think might happen. You will actually
perform each of the experiments and discover if your predictions were on the mark or
not. Write down what you honestly think will happen, so that at the end of the experiment
you can compare your ideas with what you saw. Your TA will be able to better help you
in lab if they can see from your pre-lab what ideas you have about what is going on. You
will not be graded down for wrong predictions, but you will lose points for missing
predictions.
1. Imagine that you have one battery, one light bulb and one wire. Sketch at
least one way you think you will get the bulb to light up.
2. Imagine you will have two batteries, one light bulb, and as much wire as
you want. Draw a picture of how you would connect the two batteries in
series with the light bulb.
3. Imagine that you will have two batteries, one light bulb, and as much wire
as you want. Draw a picture of how you would connect the two batteries
in parallel with the light bulb.
4. How many D cell batteries (1.5v each) do you need to get 12v? Would you put them
in series or parallel?
EXPERIMENT A: The Food Battery
1. This activity is similar to the Exploring Physics on Your Own on page 701 of Hecht.
2. You need to examine the tow set-ups and give a brief description of the following:
 materials used
 how the materials are assembled (including a sketch)
 what you observe happening
 the physics that is occurring
Questions for experiment A:
A1. What role does the lemon serve?
A2. What role does the vinegar serve? What is the difference? Could you use *anything*
in place of the lemon or vinegar?
A3. What role do the electrodes serve? Could you use any metal? Why?
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PHYSICS 1B WEEK #6
CIRCUITS WITH BATTERIES AND BULBS
Rev 1
EXPERIMENT B: One Battery, One Bulb, and One Wire
Materials:
 One battery per person
 One light bulb per person
 Several pieces of wire
1. Each person in your group should take one battery, one bulb, and one wire. Using
just these materials, make the bulb light up.
Questions for Experiment B:
B.1 Draw at least one way to make the bulb light up.
B.2 How are the arrangements that made the bulb light similar? How are they different
than the ways the bulb did not light up?
EXPERIMENT C: One Battery, One Bulb, and Two Wires
1. Each person in your group should take one battery with a holder, one bulb with a
holder, and two wires. Using just these materials, make the bulb light up.
Questions for Experiment C:
C.1 Why do we do this at all? How is this different from Experiment B?
C.2 Comparing your results with Experiment B, are the requirements the same for
lighting the bulb?
EXPERIMENT D: Two Batteries in Series with One Bulb
1. In your group, you should make two different set-ups:
 One set up will light up the bulb with just one battery (just like Experiment B).
 The other set up will connect two batteries in series with the light bulb to make it
light up.
2. Check with your TA to make sure you have the series circuit set up correctly before
answering the questions.
Questions for Experiment D:
D.1Draw the series set-up.
D.2Which bulb is brighter, the bulb in the set-up with one battery, or the bulb with two
batteries in series?
D.3Compare the current in the two circuits.
EXPERIMENT E: Two Batteries in Parallel with One Bulb
1. In your group, you should make two different set-ups:
 One set up will light up the bulb with just in parallel one battery (just like
Experiment B).
 The other set up will connect two batteries in parallel with the light bulb to make
it light up.
2. Check with your TA to make sure you have the series circuit set up correctly before
answering the questions.
Questions for Experiment E:
E.1 Draw the parallel set-up.
E.2 Which bulb is brighter: the bulb in the set-up with one battery, or the bulb with two
batteries in parallel? Or do they have the same brightness?
E.3 Compare the current in the two circuits.
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PHYSICS 1B WEEK #6
CIRCUITS WITH BATTERIES AND BULBS
Rev 1
APPENDIX: In this appendix you will explore the concepts of series and parallel circuits.
You will also learn how to use ammeters and voltmeters to measure current and voltage
in actual circuits. It is a good idea to read all the steps in each part before you start.
Questions to consider before you start:
In general to predict the relative brightness of light bulbs in a circuit one must
determine the power used by each bulb.
1. Imagine that you have one battery, two light bulbs and as much wire as you want.
Draw how you would connect the two bulbs in series with the battery. Which bulb do
you expect to be brighter? Why?
2. Again, draw two bulbs in series with one battery. On this drawing show where you
would put voltmeters to measure the potential difference across each bulb. Draw
where you would put three ammeters to check the current at three different places.
3. Imagine that you have one battery, two light bulbs and as much wire as you want.
Draw how you would connect the two bulbs in parallel with the battery. Which bulb
do you expect to be brighter? Why?
4. Again, draw two bulbs in parallel with one battery. On this drawing show where you
would put voltmeters to measure the potential difference across each bulb. Draw
where you would put three ammeters to check the current at three different places.
APPENDIX EXPERIMENT F: Bulbs in Series
Materials:
 One battery with holder per person
 Several light bulbs with holders per person
 Several pieces of wire
1. Set up two light bulbs and two batteries in series.
Questions for Experiment F:
F.1 Draw the circuit diagram for the circuit you made.
F.2 With two bulbs in series, is current “used up” in the first bulb, or is the current the
same in both bulbs?
F.3 Do you think switching the order of the bulbs will make a difference? Check!
F.4 By only observing the circuit you built, can you tell the direction of the current
through the circuit?
F.5 Is the brightness of each bulb in the two-bulb series circuit greater than, less than, or
equal to the brightness of a bulb in a single-bulb circuit?
F.6 How does the current through a bulb in a single-bulb circuit compare with the current
through the same bulb when it is connected in series with another bulb? Explain your
reasoning.
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PHYSICS 1B WEEK #6
CIRCUITS WITH BATTERIES AND BULBS
Rev 1
F.7 What does your answer to question A.4 imply about how the current through the
battery in a single bulb circuit compares to the current through the battery in a twobulb series circuit? Explain your reasoning.
F.8 Check your thinking with your TA before going on to the next part.
APPENDIX EXPERIMENT G: Bulbs in Parallel
1. Connect two bulbs in parallel with two batteries in series.
Questions for Experiment G:
G.1Draw the circuit diagram for the circuit you built.
G.2Compare the brightness of the two bulbs.
G.3What can you conclude from your observations about the amount of current through
each bulb?
G.4Is the brightness of each bulb in the two-bulb parallel circuit greater than, less than, or
equal to the brightness of a bulb in a single-bulb circuit?
G.5How does the current through a bulb in a single-bulb circuit compare with the current
through the same bulb when it is connected in parallel with another bulb? Explain
your reasoning.
G.6How does the amount of current through the battery in a single bulb circuit compares
to the current through the battery in a two-bulb parallel circuit? Explain your
reasoning.
G.7Does the amount of current through a battery seem to depend on the number of bulbs
in the circuit and how they are connected?
Brain Teaser
For identical bulbs in a single circuit relative bulb brightness is related to the amount of
current passing through each bulb. Using what you know about series and parallel
circuits, current and resistance, predict the relative brightness of each bulb in the circuit
below (rank in order from brightest to dimmest)
a
b
d
c
e
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