LESSON 8
Parallel and Series Circuits
Overview
Students will investigate how energy (in the form of electricity) flows
through different kinds of circuits and how circuits are affected by
different variables.
Student
Learning
Targets
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NGSS
MS-ETS1-1.
Background
I can describe the difference between parallel and series circuits and
when to use them.
I can tell you what causes a light bulb in a circuit to be brighter or
dimmer.
I can use a switch to open and close a circuit and tell you why it
happens.
I am able to give an example of each kind of circuit and how it is
applied in everyday life to solve a problem.
Define the criteria and constraints of a design problem with sufficient
precision to ensure a successful solution, taking into account relevant
scientific principles and potential impacts on people and the natural
environment that may limit possible solutions.
Electricity follows a pathway called a circuit. To create a circuit you need
wire, an electrical source such as a battery, and a load (the item you want
to work such as a light bulb). The electricity must be able to move from
one end of the electrical source (the battery or turbine generator) to the
load and back to the electrical source to create a complete circuit.
Electricity will only do work (example: light the bulb) when the circuit is
complete or closed. In a closed circuit electrons are able to travel without
hindrance the entire pathway (loop) via materials that conduct electricity.
In an open circuit, there is a disruption in the pathway caused by a break
in loop due to the absence of material that can easily conduct electricity
at one or more locations. Thus electrons are unable to move through
these locations and make a complete circuit. You can think of an open
circuit as a toy train track assembled to form a circle with a piece of track
missing. As the train (think of it as electrons) moves along the track, it
derails at the missing track piece and cannot complete the circle (circuit).
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A short circuit is when there is a complete circuit or loop, but the flow of
electrons takes a “short-cut” bypassing the load. Short circuits happen
when the wiring of a circuit is faulty and does not form a pathway that
must pass through the load in order to complete the circuit. If the circuit
is shorted the load will not work.
In a series circuit, electrons have only one pathway along which to flow.
A series circuit will not work if there is an opening or gap anywhere in the
circuit.
In a parallel circuit, electrons have more than one path they can take. If
part of the circuit is open, the electrons will simply follow another
pathway.
Vocabulary
circuit, load, closed circuit, short circuit, open circuit, series circuit,
parallel circuit
Resources
Energy Story – website on energy with good information explaining
circuits, batteries, etc.:
http://www.energyquest.ca.gov/story/chapter04.html
How Stuff Works – an article that helps explain how electricity is
measured and the difference between amperes, volts, and watts:
http://science.howstuffworks.com/environmental/energy/question501.htm
Materials
For each student team
5 alligator connecting wires
2 D cell batteries and battery holders *
3 mini Christmas tree bulbs (note: can use mini light bulbs and bulb
holders instead)
* Optional: can include solar panels and sun as an alternate source of
electricity in this or later lesson on photovoltaics (from lesson kits
#11, 12, and 13)
To build a simple circuit (#1 on handout), each student team needs:
Two alligator connecting wires
One D cell battery in a battery holder
One mini Xmas tree bulb with wires attached
To build a series circuit (#2 on handout), each student team needs:
Materials from #1
AND
LESSON 8 Parallel and Series Circuits
Nagele, et al. 2016
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One more alligator connecting wire
Another D cell battery
Another mini Xmas tree bulb with wires attached
To build a parallel circuit (#3 on handout), each student team needs:
Materials from #1 and #2
AND
One more alligator connecting wire
For each student
Science notebook
Pencil
Series and Parallel Electrical Circuits handout
Preparation
Prepare materials for teams and invite an electrician to the class to talk
about why she/he might use a parallel or series circuit when wiring a
home or business.
Time
60 minutes
Procedure
1. Series and Parallel Circuits Activity: Refer to overhead #1 as you
explain to students the differences between simple, series, and
parallel circuits. Share that most households are wired in parallel
circuits so that more than one appliance can be used at a time. If the
circuit to one appliance is opened (appliance shuts off) the others will
still work. Ask students: What would happen if home appliances were
wired in series? Answer: When you turned off one appliance, all the
other appliances would also go off.
2. Make sure you have materials separated for each team so that each
team can access the materials they need for #1 (circuit), #2 (series
circuit) and #3 (parallel circuit)
Assign students to small teams and distribute a copy of the “Series
and Parallel Circuits” handout, one per student.
3. Determine which student in each team will be the equipment person.
That student will get the materials for his/her team so the team can
create three circuits; first a simple circuit, then a series circuit and
then a parallel circuit (as follows):
a. Direct students’ attention to the handout challenge #1, creating a
simple circuit. Students in each team will use the #1 materials to
create a circuit; once they get the bulb to light they know they
LESSON 8 Parallel and Series Circuits
Nagele, et al. 2016
page 94
have a circuit. Each student draws and labels on their handout the
circuit their team has created. Remind students to once again use
the circuit diagram symbols in their drawings (Lesson 6, overhead
4).
b. Then the equipment person can get the materials for # 2 (on the
handout), creating a series circuit. Using both the #1 and #2
materials, students will create a series circuit; once they get both
bulbs to light – and when they remove one bulb the other bulb
also goes out - then they know they have a series circuit. Each
student draws the circuit their team has created on their handout.
c. Then the equipment person can get materials for #3 (on the
handout), creating a parallel circuit. Using all of the materials from
#1, #2 and #3, students will create a parallel circuit. Once they get
both bulbs to light – and when they remove one bulb the other
bulb stays lit – then they know they have a parallel circuit. Refer
to the illustration below for details.
Note: Have students redraw the diagrams using engineering symbols
they practiced in past lessons.
4. Review the results of each team to make sure they have created a
parallel circuit; many “first tries” result in two simple circuits rather
than a parallel circuit. A parallel circuit looks somewhat like a ladder,
one circuit is connected to the battery and the next circuit is
connected to the first circuit. Once students have achieved this
configuration, ask them to disconnect one bulb – if the other bulb
stays lit, then they have a parallel circuit.
5. Have students brainstorm where simple, series, and parallel circuits
might be of use in everyday life. One example is the new Christmas
tree lights. In the 1900s Christmas trees lights were wired in series.
When one bulb burned out, all the bulbs went out. Now with parallel
wiring, when one bulb burns out, the other bulbs stay on. If you can
find both kinds of wired Christmas tree lights, you might demonstrate
this difference for students.
Or have students Jigsaw their information (see below):
Form three (or six) student groups. Each group will be an expert on
one type of circuit: How it works, where it is used, a list of 5 examples
where the circuit can be found in every-day life, draw a diagram using
engineering symbols.
• Each student receives a portion of the materials to be introduced
aka One type of circuit.
LESSON 8 Parallel and Series Circuits
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•
•
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Students leave their "home" groups and meet in "expert" groups,
formed by the other two types of circuits.
Expert groups discuss the material and brainstorm ways in which
to present their understandings to the other members of their
“home” group.
The experts return to their “home” groups to teach their portion
of the materials and to learn from the other members of their
“home” group. Everyone tells about what they learned from the
other two circuit experts.
Career
Exploration
Invite an electrician to the classroom to talk about their job/career.
Assessment
Score “Series and Parallel Circuit” handouts.
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RESOURCES:
Short Videos that demonstrate circuit
Simple Circuit –graphic, easy to see and uses vocab words. 2:26
http://www.youtube.com/watch?v=VnnpLaKsqGU
Mr. Andersen contrasts series and parallel electrical circuits. A simulation is used to visualize
electron flow through both circuit types. Uses engineering symbols, vocabulary and discusses
Parallel and Series circuits. 8:04
http://www.youtube.com/watch?v=x2EuYqj_0Uk
Mr. Andersen describes the relationship between voltage, current and resistance in an electric
circuit. Ohm's Law is introduced through a circuit simulation. 9:46
http://www.youtube.com/watch?v=J4Vq-xHqUo8
What are Volts, OHMs & AMPSs 8:43
http://www.youtube.com/watch?v=zYS9kdS56l8
INTERACTIVE
Look inside a resistor to see how it works. Increase the battery voltage to make more electrons
flow though the resistor. Increase the resistance to block the flow of electrons. Watch the
current and resistor temperature change.
http://phet.colorado.edu/en/simulation/battery-resistor-circuit
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This is a wonderful site to explore many scientific topics. These are graphics that you can
manipulate to see what happens if you increase something or add something. Check it out!
http://phet.colorado.edu/en/simulation/battery-resistor-circuit
Explains circuits, with diagrams and interactive short quiz that matches this lesson. Interactive
topics with teacher guide and student worksheets
Circuit Symbols and Circuit Diagrams
Two Types of Connections
Series Circuits
Parallel Circuits
Combination Circuits
http://www.physicsclassroom.com/class/circuits/Lesson-4/Circuit-Symbols-and-CircuitDiagrams
EXTENSION ACTIVITIES
Education portal that has graphs, videos and information about those using electricity for their
job.
http://educationportal.com/articles/Electrician_Educational_Requirements_and_Career_Profile.html
Career site that has virtual tours, careers and education, and career Q&A. Lots of information
for students to explore.
http://www.studentscholarships.org/careers_salary/143/education/electrical_and_electronics
_engineers.php
LESSON 8 Parallel and Series Circuits
Nagele, et al. 2016
page 98