Circuits Lab 1
This is a lab that you can take home. You will need to provide your own battery (D cell, 1.5 V), but I
will provide wires and bulbs. Collaboration is acceptable, but this is meant to be done out of class.
Underlined questions = questions you need to answer, in your lab book.
Writing it up: Clearly Label “Experiment 1”, “Experiment 2,” and so on. If there is a diagram in the
instructions, copy it into your lab book. You should either write the question, or, if you like, a shorter
paraphrased version of the question before you answer it. If a drawing helps support your answer,
then draw it.
Key to Colored Text:
Red = Numbered question that you should copy (or paraphrase) into your lab book, answer, and give
your reasoning.
Blue = Instructions for a procedure that you should carry out. This might have some questions that
you should consider, but do not have to answer in your lab book.
Black = information that is helpful
Experiment 1
Obtain one battery, one light bulb, and one wire. Connect these in as many ways as you can.
Sketch each arrangement in your notebook/lab sheet. DO NOT USE ONE OF THE SOCKETS.
They are for use only in experiments 3 and 4. (1) On one side of the page, draw all
arrangements in which the bulb lights. On the other side of the page, draw all arrangements
in which the bulb does not light.
You should have sketches of at least four different arrangements that light the bulb. How are
they similar? How are they different from arrangements in which the bulb fails to light?
(2)State what requirements must be met in order for a bulb to light.
An arrangement of bulb, a battery, and a wire that allows the bulb to light is said to be a closed
electric circuit. The terms complete circuit, or just circuit are also used. The word “circuit” was
originally used to mean “ a circular route or course.”
Experiment 2
Using a bulb, a battery, and two wires, set up an electric circuit in which the bulb is lit. (3)
Does it matter which part of the bulb is connected to the end of the battery with the plus sign
on it? Explain.
In the first two experiments, you should have found that a complete circuit was necessary for a bulb to
light.
(4) Does this observation suggest that the flow in an electric circuit is one way (e.g. from
battery to bulb) or round trip (e.g. from battery to bulb and back again through the battery)?
Explain.
(5) What does your answer above suggest is a major difference between the flow in an
electric circuit and the flow of water in a river?
(6) Can you tell from your observations thus far the direction of the flow through the circuit?
Experiment 3
A. Set up a two-bulb circuit with the bulbs connected on after the
other as shown.
Two bulbs connected one after the other are said to be, “connected in
series”.
Compare the brightness of each of the bulbs with the brightness of an identical bulb in a single
bulb circuit.
(7) How does the current though a bulb in a single bulb circuit compare with the current
through the same bulb when it is connected in series with a second bulb?
B. Compare the brightness of the two bulbs in the two-bulb series circuit with each other.
(8) What can you conclude from this observation about the amount of current through each
bulb?
Pay attention to large difference you may observe, rather than minor differences that may
occur if two “identical” bulbs are, in fact, not quite identical.
C. On the basis of your observations and the reasoning you used above, respond to the
following questions:
(9) Is current “used up” in the first bulb, or is the amount of the flow the same through both
bulbs?
Do you think the order of the bulbs in this circuit might make a difference? Verify your answer
by switching the two bulbs.
(10) How does the amount of the flow through the battery in a single bulb circuit compare
with the flow through the battery in a circuit with two bulbs connected in series?
Experiment 4
A. Set up a two-bulb circuit with two identical bulbs so the
their terminals are attached together as shown.
Two bulb with their terminals attached together in this way
are said to be connected in parallel.
Compare the brightness of each of the bulbs with the brightness of an identical bulb in a singlebulb circuit.
(11) 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 parallel with a second bulb?
B. Compare the brightness of the two bulbs in the two-bulb series circuit with each other.
(12) What can you conclude from this observation about the amount of current through each
bulb?
Pay attention to large difference you may observe, rather than minor differences that may
occur if two “identical” bulbs are, in fact, not quite identical.