Transcript Toward Learning

Toward Learning and
Understanding
Electricity:
Challenging Persistent
Misconceptions
Camille L. Wainwright, PhD
Professor of Science Education
Pacific University
[email protected]
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January, 2007
Challenging
Misconceptions
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Boston Museum of Science
curriculum development:
Engineering the Future
Four units – Year-long HS course
Unit 4: “Electricity and
Communication” based on CASTLE
Electricity curriculum
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(Capacitor-Aided System for Teaching
and Learning Electricity)
Clinical Interviews (qualitative)
Pre- and Post-Assessments
(quantitative)
Refinement and re-design
following evaluation
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a. Understanding the role of
the battery as a source of
energy but not a supplier of
charge
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What is the source of the
moving charge in a circuit?
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“Charges in the circuit I believe
start at the batteries.”
(“How do you happen to know
that’s the case?”)
“Basically just growing up. The
battery is where the energy is.
If you actually put your tongue
on a battery it hurts, so I figure
that is where the electricity
comes from. I’m confident of
my answer.”
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b. Recognizing the
relationship between
energy and charge
“Are charges used up in
the production of light in a
light bulb?”
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“Yes, because if you ever touch a
bulb that has been on for awhile, it
is going to burn a little, and be hot.
So the charge is moving around and
then it converts to heat and then to
light.
“I am going to say charge is used
up, charges moving through the
filament, because if charges weren’t
used up, the battery would last
forever.”
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c. Errors due to
sequential reasoning
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“I know that if this was like a motor
or something (not a capacitor), I
know that this would be greater,
because it comes out of plus and
goes to minus, and it hits this first.”
“Regarding the position, just
looking at the pictures, the bulbs
are both the same distance, the
same position from the source, and
here Bulb A is closer to the source
of power. I figure that when the
current goes through there it won’t
be as great going to B.”
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d. Resistance of an
individual circuit
component
Bulb A glows much brighter
than B. What would you observe
if the bulbs were switched?
 “Bulb B would be brighter than
A. That is just common sense
to me. I am guessing it is the
positioning where they are, it is
not the bulbs. If you switch B
to A, B is going to be the
brighter one and A is going to
the dull position. This seems
like a ‘gimme’.”
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e. Net resistance of
series vs. parallel
resistors
Is Bulb A brighter in Figure
1 or in 2, or the same in
each?
Figure 1
Figure 2
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“ . . . and then there are two in
here in Figure 2. That is going to
use more energy for each one of
them, so A would be dimmer.”
“Bulb A will be dimmer in Figure 2
because the current is shared
between three bulbs instead
of two.”
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f. Understanding of
the circuit as a
system
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If a wire is attached
around bulb B, predict what
you would observe.
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“I would think B would actually get
dimmer, but I think bulb A would
be the same brightness.”
“I think bulb A stays about the
same brightness, because they
would both be shared, yeah.”
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g. Lack of knowledge
of internal structure
of a bulb
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In which of the following
circuits will the bulb light?
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 “B and C will light because the
circuit is complete in both of
them and there is positive and
negative. The only difference
is it is placed on a different
place on the
bulb, but I
don’t think
that matters.”
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g. Lack of knowledge
of internal structure
of a bulb
Which bulbs will light? (A & C)
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I do think that it is possible for the
current to flow from A to B and
then to C. I think that completes
the circuit. I think maybe all bulbs
will light actually.
“No bulbs will light. Some bulbs
are connected right but that
doesn’t make any difference
because B isn’t.”
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h. Understanding the
role of a compass in
circuit analysis
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Would the compass
deflection be greater at A or at
B?
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“When you have a split in the
wire, there would be a deflection
in the opposite direction. But
since these are going along the
same path, I figured they would
be in the same direction.”
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i. Imprecise
vocabulary
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“ . . . you could assume red
being the highest energy or
current or voltage or
something.”
“When you pay for a
household bill, you pay for
the energy you use, because
voltage is a measure of how
much energy is used in a
given time.”
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j. Capacitor charging
and discharging
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“Charging a capacitor, I think that
as electricity passes through it,
some of it is stored inside of the
capacitor and then the rest of it is
passed through to the rest of the
circuit.”
“The battery is going to charge up
this side, it will light this bulb A and
whatever is left will stay in the
capacitor until the capacitor is
connected and empties into bulb B
on the other side and then it cycles
again.”
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k. Circuit analysis via
color-coding
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“It will measure how much
electricity is going to the
bulb, so brightest would
be B, because it has red
going to it. Next would be
C because it has orange
energy going to it, and last
would be A, because it has
yellow. I am sure I’m
right.”
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l. Ammeters and
Voltmeters
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“Well, the ammeter wouldn’t actually
measure the current through bulb B,
because you placed it before bulb A.
“I think that the voltmeter would be
measuring the current through Bulb A . I
know that it wouldn’t be measuring the
resistance, because when we were
measuring the resistance, I think youA
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actually need a resistor in there
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to measure resistance.”
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Confidence vs.
Accuracy
(Quantitative Results)
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There was a significant
correlation between confidence
level and correctness of answer
on the Pre-Assessment.
There was no correlation
between confidence level and
correctness of answer on the
Post-Assessment. (There was a
tendency to claim confidence
even when wrong, and lack of
confidence when right -- as if
guessing.)
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Achievement Gains
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There was no significant
difference between Pre- and
Post-Assessments scores
(although scores actually
declined.)
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Achievement scores went
from 5.1 to 4.8 (out of 15
items).
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Reasons for Poor
Achievement?
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Electricity concepts are
abstract.
Time, discourse, multiple
activities are required.
Teachers must have excellent
instructional skills, including
precise vocabulary
themselves.
Curriculum developers must
have classroom teaching
experience.
Everyday experience
(“rechargeable batteries”)
Misconceptions are
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CASTLE Curriculum
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Results from research on similar
circuits following instruction
using the CASTLE Curriculum –
using a Predict/Observe/Explain
approach – have been far more
promising
Examples: Color-coding
strategies, the Hula Hoop
analogy, and the concept of
electric pressure difference (as
an alternative to ‘potential
difference’).
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Achievement
Gains ??
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Curriculum was re-designed
to include more than one
activity per concept.
Teachers had additional
professional development
and experience (same two
teachers)
Sequence of activities,
equipment choices,
layout/format were reviewed
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Achievement Gains:
Year 2 ??
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Clinical interviews (qualitative
results) often showed similar
misconceptions
However, quantitative results
(pre- and post-assessment)
showed significant gains
(n = 52) with no significant
difference between two
teachers
Pre-Assessment Mean: 4.46
Post-Assessment Mean: 9.28
p < 0.001
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