Session F1D
INQUIRY-BASED EXPERIMENTS IN THE INTRODUCTORY PHYSICS
LABORATORY
Robert Ross1
Abstract  This paper will describe a significant effort to
improve the second semester general physics laboratory at
the University of Detroit Mercy by incorporating inquirybased laboratory experiments.
The inquiry-based
laboratory experiments are modeled on published research
results.
We require the students to confront their
misconceptions by directing them through a process of
inquiry. The students use simple and inexpensive materials
to perform experiments on direct-current circuits, magnets,
electromagnetism, and optics. They use these experiments to
develop operational definitions for technical terms,
construct models of the relevant physical phenomena and
apply the models in new situations to test their predictive
capability. This paper will describe some of the laboratory
experiments, and describe their effect on student outcomes.
Student attitudes toward these laboratory exercises will also
be presented.
Index Terms  Circuits, inquiry-based, laboratory,
physics.
PRESENT SITUATION AND STRATEGY
There is no shortage of data that shows that students emerge
from introductory physics courses with a poor conceptual
understanding. In recent years much effort has gone into
trying to understand the causes of these difficulties and to
find remedies [1]. The Physics Education Group at the
University of Washington has developed a curriculum that is
more effective than traditional lecture materials. These
materials are inquiry-based and use tutorials to guide
students through activities that are shown to develop a solid
conceptual framework [2,3]. Laboratory-based curricular
materials have been developed by other groups and have
been shown to be quite effective [4,5].
To fully implement these types of curricular
improvements requires the adoption of laboratory based
instruction or tutorial sessions. At the present time our
college is unable to implement such massive change.
Switching to a laboratory-based curriculum requires adding
additional laboratory sessions, which is not practical at the
present time. The tutorial sessions require frequent meetings
in small groups. These changes would require additional
laboratory space and faculty. Instead, our strategy has been
to institute a change in our laboratory instruction. We have
developed a laboratory curriculum based on the references
cited above to improve the instruction of the second
semester general physics laboratory. Our introductory
physics sequence consists of large group meetings (lecture)
3 to 4 times a week and one 3-hour laboratory session each
week. The calculus based engineering and science physics
sequence meets 4 times each week while the algebra-based
pre-medical/pre-dental physics sequence meets 3 times each
week.
Electric circuits are introduced very early in the
elementary education curriculum. Several times during their
primary and secondary schooling students have seen
diagrams of complete electric circuits and cross-sectional
views of flashlights. They have seen sketches of circuits
with batteries and light bulbs. It would seem that the
concepts of complete circuits and a rudimentary
understanding of current flow would be well understood by
college students. Nothing could be further from the truth.
Most students, up to 60%, have absolutely no experience
with real circuits [6].
Our strategy is to provide students with a hands-on
experience. We provide simple, inexpensive materials such
as lantern batteries, flashlight bulbs, light bulb sockets,
connecting wire and switches and guide the students though
a series of activities. The activities are structured to force
the students to think about the circuits, develop mental
models and apply these models in new situations. We give
them an opportunity to set up circuits, observe the behavior
of flashlight bulbs in different circumstances and make
predictions about what will happen as changes are made to
the circuit. They are encouraged to predict honestly and
they are not penalized for making incorrect predictions. As
they proceed through the workbook they answer questions
and describe the reasoning that they use to explain the
behavior of the circuits and make their predictions.
We believe that for the students to have a functional
understanding of new concepts it is generally necessary for
them to develop operational definitions of technical terms.
They must also explain their reasoning verbally either to
their instructor or to their lab partners. We require them to
do this during the course of their laboratory assignments.
They spend much more time writing down their explanations
than they do making calculations. We believe that it is
necessary to lead the students from patterns of concrete
thinking toward those of formal or abstract reasoning. They
need practice distinguishing observation from inference and
in applying inductive forms of reasoning instead of only
deductive ones.
1
Robert Ross, University of Detroit Mercy, Department of Electrical and Computer Engineering, 4001 W. McNichols, Detroit, MI 48219,
rossra@udmercy.edu.
0-7803-6424-4/00/$10.00 © 2000 IEEE
October 18 - 21, 2000 Kansas City, MO
30 th ASEE/IEEE Frontiers in Education Conference
F1D-1
Session F1D
INQUIRY-BASED EXPERIMENTS
Electricity: Students develop operational definitions for
complete circuits, conductors, and insulators. They develop
the important hypothesis that the brightness of a light bulb is
related to the amount of current flowing through it. They
explore the concept of current as it relates to flow. The
students distinguish between the concepts of speed and the
concepts of quantity of flow. They are introduced to
schematic representations of electric circuits.
Electric Current and Circuits: Students develop an
operational definition of electric current based on its effect
on a light bulb. They use an indicator bulb to measure the
current through a battery and observe the effects of different
circuit configurations. They also develop the concepts of
resistance and equivalent resistance.
Series and Parallel Networks: Students identify series and
parallel configurations of light bulbs. They practice relating
the physical configurations to the schematic ones, and
recognize that they bear little resemblance to each other.
Electrical Measurements I – Current: Students use a
magnetic compass to investigate the relationship between the
current flow in a wire and the deflection of a nearby
compass needle. This relationship is exploited to develop a
model for the behavior of a d’Arsonval galvanometer. The
ability to measure the amount of current flowing leads to the
development of an operational definition for electrical
resistance.
Electrical Measurements II – Voltage and Resistance: The
students investigate the properties of a voltmeter and
measure the voltage differences between parts of a circuit.
They develop the correct definition of resistance and apply it
to situations where the resistance is constant, Ohm’s Law,
and where the resistance depends on the current, a light bulb.
Electric Power and Kirchoff’s Second Law: The students
apply their models for current, voltage and resistance to a
new situation, one where light bulbs have different
resistance. They recognize that the original current model is
inadequate to describe the effect of having bulbs with
different resistance in series. They develop the correct
relationship that relates the brightness of the bulb to the
power it dissipates. They apply Kirchoff’s voltage law to a
variety of situations and observe that voltage differences
often exist across the terminals of an open switch.
Circuits Containing Resistors and Capacitors: Students use
large valued electrolytic capacitors to visualize the effects of
capacitors in circuits. They apply Kirchoff’s rules and the
definition of capacitance to predict the behavior of circuits
with light bulbs and capacitors. They investigate the
relationship between the circuit conditions and the time it
takes for the capacitor to charge and discharge.
Magnetic Fields: The students map the magnetic field due
to various configurations of permanent magnets with
magnetic compasses. They relate the strength of the field to
the configuration of field lines. They develop an operational
definition for the field and recognize the applicability of the
principle of superposition.
Electromagnetic Induction: The students develop a method
to determine the magnetic field due to a current carrying coil
of wire. They compare the current carrying coil of wire to a
bar magnet and develop a rule to relate the direction of the
current flow to the direction and strength of the magnetic
field. They investigate the effect of a changing magnetic
field on a coil of wire. They develop a method to vary the
magnetic field through a solenoid and study how the
direction of the changing field effects the direction and
strength of the induced current.
Tracing Light Rays: The students develop the concepts of
light rays and practice drawing ray diagrams to locate the
image of various objects. They investigate the properties of
converging and diverging optical elements such as lenses
and mirrors.
Image Formation and Lenses: The students develop
operational definitions for images and see how images are
formed by different optical elements like lenses and
pinholes. They investigate the role of the lens in image
formation and measure the focal properties of converging
lenses.
The Optical Principles of the Eye: Using a model of the
human eye, the students explore image formation on the
retina. They describe typical vision defects. They use
lenses to correct the common vision defects.
The next sections describe three of the experimental
procedures in detail. Some of the results of the student
experiments are also reported.
EXPERIMENT #1-ELECTRICITY
The first experiment that the students perform is designed to
develop the concept of a closed or complete electric circuit.
The students are given a lantern battery, 20 cm of copper
wire, and a flashlight bulb. They are instructed that they
need to find three different ways to light the bulb using all
three of the components. The students are told that time is
not a factor and that the amount of time that it takes to light
the bulb does not affect their grade or cast aspersions on
their intellect or ability. Each time this activity is performed
the instructor is amazed that it takes about 45 minutes before
everyone in the class has accomplished the task. Contrary to
the observations of some other groups, it appears that the
best predictor for the time it takes to complete this activity is
prior experience [7].
The students are asked to sketch three different
arrangements of the components that cause the bulb to light
and also three that do not. They are then asked to write a set
of instructions that someone unfamiliar with the equipment
could follow to light the bulb. By performing this activity
the students have developed an operational definition of a
complete circuit. They recognize that the bulb and battery
each have two separate ends or terminals. They discover
0-7803-6424-4/00/$10.00 © 2000 IEEE
October 18 - 21, 2000 Kansas City, MO
30 th ASEE/IEEE Frontiers in Education Conference
F1D-2
Session F1D
that it is necessary to use each of these terminals to complete
the circuit.
After the students have developed an operational
definition of a complete circuit, the students test various
materials to observe their effect when placed in the path of
the current. This experiment develops the concepts of
conductor and nonconductor or insulator. The students
recognize that the meaning of these technical terms is
contained in the concrete experience of seeing the light bulb
glow. There is no meaningless jargon such as “conductors
allow electrons to pass through.” The purpose here is to
have the students discover that in order for the bulb to light
it is necessary to have a continuous path of metal from one
terminal of the battery to one terminal of the bulb and from
the other terminal of the battery to the other terminal of the
bulb. This concept is crucial to the development of the
concept of current.
The final part of the introductory experiment is to draw
cross-sections of an ordinary household light bulb and light
bulb socket. To facilitate these drawings the students are
encouraged to break the glass envelope of the light bulb and
examine the interior. They are required to pay strict
attention to the wires connecting to the filament and to
indicate where these wires terminate. They are also
provided with a disassembled bulb socket. The result of this
activity is that over half of the students are surprised that the
filament is connected to the side of the metallic base and
also to the metallic tip on the bottom of the bulb. They
observe that the socket has two terminals. They see, many
for the first time that the socket does not simply allow the tip
of the bulb to come into contact with “the electricity in the
wire.” The students discover that the bulb must be in the
socket in order to have a continuous path of metal from one
side of the socket to the other. Often they verbalize that they
now understand how Christmas lights work.
The concept of an electric current is introduced with the
analogy to the flow of water. The students are familiar with
this concept but must be made to carefully distinguish
between some closely related concepts. They need to
compare how the speed of the water is related to the quantity
of flow. They need to state what happens when water flows
through a pipe or down a river. They need to recognize that
as the water flows its speed can change but the quantity of
flow remains constant. As the fluid reaches a branch it has
the opportunity to split and the total amount into the junction
is the sum of the amounts through each branch. We
emphasize that these concepts are all equivalent when we
consider an electric current instead of a current of water.
We infer that the light bulb lights only when an electric
current is present. While we cannot see, hear, or feel the
current we hypothesize its existence to explain the observed
behavior of the battery and bulb. Furthermore, they
hypothesize that the brightness of the bulb is an indication of
the amount of current flowing through it. We are careful not
to say that we expect that the brightness is proportional to
the current, just that brightness is an indication of the
amount of flow.
The students are asked to connect a bulb to the battery
as shown in the figure and to compare the current at different
locations in the circuit. We are trying to disabuse them of
the notion that the current is used up in certain elements of
the circuit.
FIGURE 1. A CIRCUIT WITH A BATTE RY AND BULB.
Next they are asked to predict the relative brightness of
two bulbs in a series circuit shown below. They are also
asked to predict the brightness of each bulb in relation to the
bulb from the single bulb circuit. After they complete the
circuit and observe what happens, they are to compare the
current flow in the two-bulb circuit with the current flow in
the single bulb circuit.
FIGURE 2. A CIRCUIT WITH A BATTE RY AND TWO BULBS IN SERIES.
They observe that the two bulbs are of equal brightness
and dimmer than the single bulb case. Many students
interpret this as being caused by the bulbs using up s ome of
the current. This misconception is partially due to the belief
that the battery always supplies a constant current. They are
led to compare the brightness of each bulb and interpret this
in accordance to our hypothesis of the relation between the
brightness of the bulb and the amount of the current. Then
they are asked to infer the amount of current flowing in the
battery in this case and compare it to the current flowing
through the battery in the case of the single bulb circuit.
Finally, they are asked to predict the relative brightness
of two bulbs in a parallel circuit. This circuit is shown
below in Figure 3. They are also asked to predict the
brightness of each bulb in relation to the bulb from the single
bulb circuit. After they complete the circuit and observe
what happens, they are to compare the current flow in this
two-bulb circuit with the current flow in the single bulb
circuit.
They observe that the two bulbs are of equal brightness
and equal to the single bulb case. They are forced to
conclude that the current flow through each bulb is the same,
and is also the same as that through the single bulb in the
one-bulb circuit. They are asked to infer the quantity of
current flowing through the battery in this case and compare
it to the current through the battery in the single-bulb and
series cases.
0-7803-6424-4/00/$10.00 © 2000 IEEE
October 18 - 21, 2000 Kansas City, MO
30 th ASEE/IEEE Frontiers in Education Conference
F1D-3
Session F1D
that the addition of more resistors in this parallel
configuration causes the total resistance to decrease.
FIGURE 3. A CIRCUIT WITH A BATTE RY AND TWO BULBS IN PARALLEL .
To reinforce how their model of electric current can be
used to explain the behavior of these circuits, the students
are asked to summarize their conclusions about the current
flow in each of these cases. They are to clearly discuss how
they believe the current flows through the battery, how it
splits up at a junction and how the amount of current
correlates with the observed brightness. They are asked to
estimate the relative time each battery will last in the
different cases under consideration. Many students use their
model of electric current to correctly predict that the parallel
combination will last the least amount of time because it
corresponds to the case with the largest amount of current
flowing through the battery. It is however, not uncommon
for students to predict the lifetime of the battery to be equal
in the single-bulb and 2-bulb series cases. They verbalize
that since the current is the same in a series circuit, it must
be the same as the single bulb case and so the battery should
last the same amount of time. It appears that these students
misrepresent the meaning of the word same. They interpret
same to mean the same at all times, when in fact the correct
interpretation is that in a series circuit the current is believed
to be the same at all places.
EXPERIMENT #2- ELECTRIC CURRENT AND
CIRCUITS
The second experiment that the students perform continues
to reinforce the concept of current. They connect a light
bulb to the battery and use this bulb as an indicator bulb.
This indicator bulb measures the current flowing through the
battery; the brighter the indicator bulb the more current that
flows through the battery. Next they build a series circuit
with two identical bulbs as they did before, but this time
they include a single-pole single-throw switch. They predict
what will happen and interpret the results in accordance to
their model of current flow. They usually indicate correctly
that the indicator bulb will dim. This observation is used to
introduce the concept of resistance.
Each bulb has
resistance; it resists or impedes the flow of current through
it. The dimming of the bulb indicates a reduction of current
through it and hence through the battery. They explain that
adding bulbs in series increases the resistance and causes the
current to decrease. They add an additional bulb in parallel
with one of the bulbs and predict how the brightness of the
bulbs will change. Most students are surprised that the
indicator bulb brightens. They are now able to correctly
interpret what is happening in this situation. They recognize
Indicator bulb
FIGURE 4. A CIRCUIT WITH A BATTE RY AND AN INDICATOR BULBINSERIES
WITH TWO BULBS IN PARALLEL .
The model of electric current flow the students
developed is adequate to allow them to predict the relative
brightness of the bulbs shown in the circuit below in Figure
5. They can correctly predict that A=B>C=D=E by noting
that bulbs A and B each receive half of the current coming
out of the battery while C, D and E each receive only onethird. They are then asked to predict what will happen if any
of the bulb C, D, or E are unscrewed from their sockets.
When the model is applied correctly, the students are able to
predict that since we are unscrewing one of the bulbs C, D,
or E, we are removing a parallel branch from the circuit and
the current through the battery should decrease. Since the
current decreases A and B should dim. Furthermore, since
the current only splits in half for the remaining branch
instead of into thirds, the remaining bulbs (2 of C, D or E)
must brighten.
A
B
C
D
E
FIGURE 5. A CIRCUIT WITH A BATTE RY AND TWO PARALLEL COMBINATIONS
OF BULBS.
Each semester a few of the more observant students
recognize that something is amiss with this analysis. They
realize that removing a parallel branch causes the current to
decrease through the battery. If the current decreases and
yet a path is removed, how do we know that C, D or E must
brighten? Why do they not remain the same? This type of
questioning will eventually show why we need to modify
our model of current flow to include the concept of potential
and potential difference.
0-7803-6424-4/00/$10.00 © 2000 IEEE
October 18 - 21, 2000 Kansas City, MO
30 th ASEE/IEEE Frontiers in Education Conference
F1D-4
Session F1D
EXPERIMENT #9- ELECTROMAGNETIC
INDUCTION
Electromagnetic induction is one of the most difficult topics
covered in the introductory course. In order to use Lenz’
Law, students are required to keep track of the strength and
direction of a magnetic field, keep track of the magnetic
flux, and recognize how the magnetic flux changes. They
need to understand how the direction of a magnetic field is
related to the direction of the current flow in a wire. Many
students cannot develop this pattern of formal reasoning.
The situation is complicated by their inability to visualize
the multiple changes taking place.
Consider the situation shown in Figure 6 where we
show an ordinary bar magnet and a coil of wire. The
students have previously determined that the magnetic field
points away from the north pole of a bar magnet. They have
also determined that the field strength is greatest in the
region of space near the poles.
v
B
S
v
S
N
N
B
FIGURE 6. A BAR MAGNET NEXT TO A LOOP OF WIRE .
Most of the students can correctly indicate the direction
of the field due to the magnet at the location of the loop of
wire. They can also correctly determine that the field
strength decreases if the magnet is moved to the left. A
significant number incorrectly assume that the direction of
the field changes to point toward the left if the magnet is
moved to the left. It seems as if they are confused the
arrows used to represent the direction of the field and the
arrows used to represent the direction of motion of the
magnet.
The students use a solenoid to produce a magnetic field.
They use a compass to determine the direction of the field
and develop a rule that relates the direction of the current
flow to the direction of the field. They are then led to
describe what happens to the current though the coil as a
current controlling switch is opened and closed. They need
to verbalize that the process of closing the switch causes the
current to increase and that the increasing current causes the
magnetic field to increase. They need to recognize that
opening the switch causes a corresponding decrease in the
magnetic field strength.
Next the students use a galvanometer to measure the
current induced in a 1000 turn secondary transformer coil
when the primary solenoid is inside of it. They use the
galvanometer to determine the direction of current that is
induced in the secondary coil. This proves to be especially
difficult, the students are able to see the direction in which
the coil is wound but they have difficulty in recognizing
from which terminal the current emerges. Once they have
correlated the direction of current flow with the reading on
the meter they can proceed to relate how the changing
magnetic flux induces current.
STUDENT ATTITUDES
Students generally seem to like the laboratory experiments.
They are required to hand in their work at the end of the
session so they have no homework. The students were asked
to comment on the question, “What factors about the
COURSE ITSELF make this class a good learning
experience?” on the end of the semester course evaluations.
Some relevant samples of student comments are included
below:
• Lab was effective in learning concepts for PHY 162
lecture.
• I think we should take the material before we do the lab.
• It provided actual hands on learning, was related to
classroom teachings.
• Hands on, interesting, let us think independently.
• It put the physics learned in class to practical
application.
• Put abstract ideas into perspective. Challenged students
to think independently.
• Labs were sometimes difficult to comprehend.
• It was set up to make you think. I learned more in this
lab than in lecture, and I’ll actually remember it because
I had to figure things out myself. That is an excellent
way to learn.
• I was forced to apply my intellect in order to succeed in
this class. Logic and applied concepts were useful.
CONCLUSIONS
Inquiry-based laboratory experiments are more useful in
engaging the students to use higher level thinking skills then
typical “cookbook” type laboratory experiments. When
students use the inquiry methods they seem to be more
willing to take responsibility for their own learning. The
exercises also provide important experience to students who
have never had an opportunity to experiment first hand with
common direct current circuits.
REFERENCES
[1]
For a recent review of the literature on physics education research see:
McDermott, L.C., Redish, E.F., “Resource Letter: PER-1: Physics
Education Research”, Am. J. Phys., 67, 9, Sept 1999, 755.
[2]
McDermott, L.C. and the Physics Education Group at the University
of Washington, Physics by Inquiry Vols. I and II. Wiley, New York,
1996.
[3]
McDermott, L.C. and the Physics Education Group at the University
of Washington, Tutorials in Introductory Physics, preliminary
volume. Prentice-Hall, Upper Saddle River, NJ, 1998.
0-7803-6424-4/00/$10.00 © 2000 IEEE
October 18 - 21, 2000 Kansas City, MO
30 th ASEE/IEEE Frontiers in Education Conference
F1D-5
Session F1D
[4]
Laws, P., Workshop Physics Activity Guide. Wiley, New York, 1997.
[5]
Laws, P., “Calculus-based physics without lectures”, Physics Today,
44, 12, 1991, 24.
[6]
McDermott, L.C., Shaffer, P.S., “Research as a guide to curriculum
development: An example from introductory electricity. Part I:
Investigation of student understanding”, Am. J. Phys., 60, 11, Nov
1992, 994.
[7]
Brown, T.R., Slater, T .F., and Adams. J.P., “Gender differences with
batteries and bulbs”, The Physics Teacher, 36, 9, Dec 1998, 527.
0-7803-6424-4/00/$10.00 © 2000 IEEE
October 18 - 21, 2000 Kansas City, MO
30 th ASEE/IEEE Frontiers in Education Conference
F1D-6