Lesson Plan: Introduction to Parallel Circuits
Unit: Electromagnetism Component: 3. Series and Parallel Circuits
Date / Day: Monday, April 8th, 2013 - Day 1
Block / Time Available: A Block, 7:45 - 8:43 (58 min)
Objectives and Assessment
Content Objective:
You will be able to describe how charges and energy flow
in a parallel circuit.
Language Objective:
Students can express in written form the causal
relationship between relative resistance and relative
current in a parallel circuit.
Criteria for Success / Assessment:
● Can I describe what happens to the current in a
circuit when there is more than one path that the
current can take?
● Can I describe what happens to the voltage in a
circuit when there is more than one path for the
current to take?
Language Learning:
Student ideas will be affirmed in their own words during
discussion and revoiced using academic language.
Language Assessment:
Student final explanation on handout.
Assessed on exit ticket (last three questions of handout).
LESSON AGENDA
Phase
& Criteria
ELICIT
(T.1G)
TEACHER
Do Now is put up on the board.
Provide/display a circuit diagram
of a basic parallel circuit (two
equal resistors), with the positive
branch point labeled Point A.
Brief share out of ideas, especially
on Question 1. Get a couple of
ideas out for questions 2 and 3,
then demonstrate by checking on
a circuit board under the
document camera (thereby also
demonstrating once again proper
use of the multimeter).
STUDENTS
Students will write
individual responses to
the questions:
1. Describe how current
moves through this
circuit. What do you think
happens when the
charges reach Point A?
2. Do you think the
current is the same or
different through the two
resistors? Why?
3. Do you think that
voltage will be the same
or different across the
two resistors? Why?
Student Ideas and
Engagement
Time
I anticipate that [specific
students] will need some
prodding to get engaged
with the content during
the Do Now.
12 min
Students may answer:
The charges split in two.
All of the charges take
the first path. They will
likely say that current is
the same. They may or
may not think that the
voltage is the same.
ENGAGE
T.3A
Frame the day by showing the
objective and CFS on the board.
Check for student understanding.
Student will predict what
What do you think
today is going to look like. “parallel” means in a
circuit?
1 min
Show a new parallel circuit, this
one with two different resistors.
Ask students to write down their
individual responses.
Students will answer
individually:
1. Describe how current
moves through this
circuit. What do you think
happens when the
charges reach Point A?
2. Do you think the
current is the same or
different through the two
resistors? Why?
3. Do you think that
voltage will be the same
or different across the
two resistors? Why?
Students may say:
3 min
Ask students to compare their
ideas to each other. See if you
can come to an agreement at your
table about these questions. It’s
ok if you disagree, but make sure
you discuss why.
Students will discuss in
table groups for 2
minutes.
(Ask co-resident to look
for competing theories,
especially a group that
has internal division.)
2 min
Go around to each group in turn
and have them share their
model(s) with the class. No classwide discussion at this time, save
it for after we see what happens.
One student from each
group will share their
model. We will take 5
minutes to get each
group’s initial models and
explanations on the
board.
If co-resident or I find a
group with internal
divisions, ask a student
to compare his/her idea
to the other idea. If
opportune, request that
student ask
clarifying/probing
question of the other
student.
5 min
EXPLORE
What is the best way to see if our
ideas are correct? We test them!
T.1A, T.1G
Display a circuit diagram for a
parallel circuit with two different
resistors.
Students will measure the Students may be
current through each path confused about use of
in the parallel circuit (2
the multimeter.
different resistances).
If students seem to be
confused about the
Students will calculate the multimeters pause their
voltage across the two
exploration briefly to
resistors using Ohm’s
review how to measure
Law.
each. This is also an
We are going to predict. (Record
this on the board).
T.2B
T.1H, T.2G
T.3B, T.3C,
Go around and find a group of
students who are getting correct
All charges will go down
the easier path, because
there is less resistance
and they wouldn’t
choose to take a harder
path. Some charges will
go down both paths, but
fewer charges go down
the harder path. More
charges need to go down
the harder path because
it will take more of them
to beat the higher
resistance. The current
will probably be different
through the different
resistors because one is
harder to move through.
The voltage will be
different because they
are different resistances
and Ohm’s Law says the
voltage should change.
NLT
8:10
15 min
T.1H
or interesting results. Talk to them
about their process and ideas. Ask
if they would share their findings.
opportunity for
demonstrating how we
learn from mistakes if we
get nonsensical values.
Answer the following
questions on your
handout:
Compare the voltages
across the two resistors.
How do you explain your
findings?
Compare the currents
through the two resistors.
How do you explain your
findings?
EXPLAIN
T.1B, T.1C,
T.1E, T.1F,
T.2G
Begin a mini discussion. Who
would like to share what their
group discovered?
Students will share out as
a class and discuss their
findings in light of their
initial models.
What happened to the current?
Does this make sense? How does
this compare to our initial ideas
about what would happen?
Why was the voltage the same?
What does this mean for the
charges and for the energy in the
circuit?
Arrive at a new model of
the phenomenon.
Bring discussion to a close when
we have reached something close
to a scientifically accurate
explanation. Clarify end objective
knowledge if necessary (using
height analogy for example)..
ELABORATE
We will be exploring parallel
circuits for the next couple of
days.
EVALUATE
Distribute exit ticket:
Collect exit tickets and handouts.
NLT
8:25
10 min
Build on each others’
ideas.
Press students to pose clarifying
and probing questions to each
other. Can do this by providing
example sentence stems on the
board, and referring to them.
Use a table on the board to
summarize information.
As students present
ideas in their own terms,
clarify and rephrase
using academic
language, paying
particular attention to
causality.
Answering exit tickets.
End objective of the
discussion: 1) Current is
split between the
available paths, inversely
proportional to the
relative resistances.
More current flows
through lower resistance.
2) Energy per charge lost
is the same on all
pathways, regardless of
resistance..
10 min
How was assessment used to inform instruction?
Exit ticket 4/2/13 assessed students understanding of Ohm’s Law after the first lesson in which it was introduced. Just
over 40% of students used the equation correctly, indicating that more practice is needed. This was my baseline for
seeing how their understanding of Ohm’s Law was progressing over the course of the unit component.
Exit ticket 4/4/13 was taken after multiple entry points in several lesson on Ohm’s Law. By this time 71.4% of students
calculated correctly using Ohm’s Law. Most of those who got it wrong were math errors (solving for part of a fraction).
On the second question, students were asked whether they thought that a circuit with a single 2-ohm resistor would
have the same or different current as a series circuit with 2 1-ohm resistors. The class was about about evenly divided
between the two answers, suggesting that there are many misconceptions that will make for a rich discussion and
opportunities for learning when multiple resistors are added. This will be the first time they will analyze a circuit with
more than one component.
Lab handout from 4/3/13 shows evidence that some students are still having trouble with the multimeters, which are
confusing with all the modes. Consulting LI notes from CT and video, we noted that all three teachers were circulating
and helping many students with multimeter questions, and this was taking up a lot of time and causing distraction. This
lesson has been designed to use only one multimeter mode, current measurement. Instead of measuring voltage, they
will be given the resistance and get practice with Ohm’s Law in calculating the voltage. This should be fine as previous
data shows that most of the class can calculate using Ohm’s Law, and they will be in groups and can help each other.
Content Goals
Students will be able to qualitatively explain how charges and energy move through a simple parallel circuit. The two
major content understandings of the lesson are:
● The total current in a circuit is split among parallel pathways, in a distribution that is inversely proportional to
the relative resistances of those pathways.
● The voltage (energy lost per charge) across all pathways is the same.
Massachusetts State Standards:
● 5.3 Analyze simple arrangements of electrical components in both series and parallel circuits. Recognize
symbols and understand the functions of common circuit elements (battery, connecting wire, switch, fuse,
resistance) in a schematic diagram.
Relevant NGSS Science and Engineering Practices:
● 1. Asking questions (for science) and defining problems (for engineering)
● 2. Developing and using models
● 3. Planning and carrying out investigations
● 6. Constructing explanations (for science) and designing solutions (for engineering)
● 8. Obtaining, evaluating, and communicating information
Lesson plan by Nalin A. Ratnayake. Free to distribute, modify, and use for non-commercial purposes. Please credit
the author.