Physics 1B
• BATTERIES AND LIGHT BULBS •
Rev 3-AH
Introduction
This lab relates to material in Hecht, Chapter 17. 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 Experiment A and your group will need to cycle
through that station at some point during the lab. Material in this lab has been adapted from
McDermott, Tutorials in Introductory Physics.
Pre-Lab Homework
These Pre-Lab Homework problems are to be done before you get to lab. They are predictions –
your hypotheses – of what might happen. You will actually perform each of the experiments and
discover if your predictions were correct. 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’s 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 piece of wire that cannot be cut. Sketch
at least one way to connect these components in order to get the bulb to light up.
2. Imagine you 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 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 (1.5 V each) do you need to get 12 V? Would you put them in series
or parallel?
Experiment A: The Food Battery
This activity is similar to the “Exploring Physics on Your Own” on pg. 701 of Hecht.
Examine the two setups and give a brief description of the following:
• Materials used
• Assembly of the materials (including a sketch)
• What you observe happening
• The physics that is occurring
Questions:
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 metals? Why or why not?
© 2001 UCSD-PERG
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Physics 1B
• BATTERIES AND LIGHT BULBS •
Rev 3-AH
Experiment B: One Battery, One Bulb, and One Wire
This experiment should be performed in groups of two. The following materials and procedure
apply for each group of two.
Materials:
• One battery (not in its holder)
• One light bulb (not in its holder)
• One piece of wire
Procedure:
1. If the battery and/or light bulb is already in a holder, remove it from its holder, and set the
holder aside.
2. Using only the materials specified above, determine an arrangement that will make the bulb
light up.
3. Confer with the rest of the group (or the TA) until you have discovered and tested all four
possible arrangements.
Questions:
B1. Draw at least one way to make the bulb light up.
B2. 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
As in Experiment B, this experiment is to be performed in groups of two.
Materials and Procedure:
• One battery and battery holder
• One light bulb and light bulb holder
• Two wires (already connected to the battery holder)
Using just these materials, determine an arrangement to make the bulb light up.
Questions:
C1. How is this setup different from Experiment B? What advantages are there to this setup?
(i.e., Why do we do this at all?)
C2. Comparing your results with Experiment B, are the requirements the same for lighting the
bulb?
© 2001 UCSD-PERG
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Physics 1B
• BATTERIES AND LIGHT BULBS •
Rev 3-AH
Experiment D: Two Batteries in Series with One Bulb
Procedure:
1. In your group, make two different setups:
(a) Connect one battery to make the bulb light up (as in Experiment B or C).
(b) Connect two batteries in series with the bulb to make it light up.
2. Check with your TA to make sure you have the series circuit set up properly before
answering the questions.
Questions:
D1. Draw the series setup (b).
D2. Which bulb is brighter, the bulb in the set-up with one battery, or the bulb with two
batteries in series?
D3. How does the current through the light bulb correlate to the brightness of the bulb?
D4. Compare the current through the light bulb in the series circuit to the circuit with just one
battery.
D5. Compare the current supplied by the battery in the series circuit to the circuit with just one
battery.
Experiment E: Two Batteries in Parallel with One Bulb
Procedure:
1. In your group, make two different setups:
(a) Connect one battery to make the bulb light up (again, as in Experiment B or C).
(b) 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 parallel circuit set up properly before
answering the questions.
Questions:
E1. Draw the parallel set-up (b).
E2. Which bulb is brighter – the bulb in the setup with one battery, or the bulb with two
batteries in parallel? Or, do they have the same brightness?
E3. For both circuits (a) and (b), compare the voltage across the light bulb.
E4. Compare the current through the light bulb in the parallel circuit to the circuit with one
battery. Is this consistent with your answer to D3?
E5. Compare the current supplied by each battery in the parallel circuit to the circuit with one
battery.
E6. Why is this sort of circuit (batteries in parallel) desirable or advantageous?
E7. Why is the circuit in Experiment D (batteries in series) advantageous?
When you are finished exploring and experimenting with different circuits, please clean up all
your equipment and place it in the box as you found it.
© 2001 UCSD-PERG
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