LESSON 6
Current Electricity – Circuits and Switches
Overview
Students will explore how current electricity travels in pathways called circuits.
Students will create a working circuit using a light bulb, battery, two types of
switches, and wire.
Student
Learning
Targets
•
•
•
•
I can define the terms “circuit” and “current electricity” and tell you where we
used them in everyday life.
I can describe the difference between closed, open, and short circuits as
applied to real life situations.
I can show you how a switch works and why switches are important.
I can explain electrical insulator and conductor and give several examples of
each.
NGSS
None
Background
Like static electricity, current electricity involves the movement of electrons. The
difference is that in current electricity electrons move from atom to atom along 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 or
motor). The electricity must be able to move from one end of the electrical source
(the battery, turbine generator or photovoltaic panel) to the load and back to the
electrical source to create a complete circuit. Electricity will only do work
(example: light the bulb or run a motor) when it is complete or closed. In a closed
circuit electrons are able to travel the entire pathway (loop) without hindrance via
materials that conduct electricity.
In an open circuit, there is a disruption in the pathway caused by a break in the
loop because of the absence of material that can easily conduct electricity. 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).
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
LESSON 6 Current Electricity – Circuits and Switches
Nagele, et al. 2016
page 69
order to complete the circuit. If the circuit is shorted, the load will not work. For
example, if the load is a bulb it will not light because it is not receiving the
electricity (electrons).
The wires we will be using are made of copper or aluminum, which are conductors
(they readily transmit electricity). The wire is coated with plastic; an insulator
(does not allow any significant flow of electrical current). Everyday materials are
divided into two groups: conductors and insulators. Most metals like copper,
aluminum, iron, zinc and steel are conductors. Water is also a fairly good
conductor, especially if it contains minerals and/or electrolytes. Insulating
materials include rubber, plastic, glass, and wood.
Students will be using such low levels of electricity that safety is not a concern.
The electricity will flow from the electrical source (battery) through the wires to
the load (light bulb).
In everyday use of electricity, humans use switches to turn on and off the flow of
electricity to electrical devices. The switch is an important part of the circuit even
though it is a simple concept. The switch in a circuit merely allows one to open or
close the circuit, controlling the flow of electrons along the pathway. If one turns
the switch on, the switch closes the circuit allowing electricity to flow. Turn the
switch off and it opens the circuit – electrons can’t cross the tiny space created
inside the switch. The three kinds of switches provided in the following activity will
allow students to explore the way “on” switches allow a closed circuit to be
created and “off” switches allow an open circuit to be created.
Project overhead #1 titled: “Definitions” on the screen and ask students to write
these definitions in their science notebooks.
DEFINITIONS
electricity: the flow of electrons (in atoms) in a circuit
circuit: a pathway for electricity that includes a wire, an electrical source and a
load (like a light bulb)
open circuit:
Battery
LESSON 6 Current Electricity – Circuits and Switches
Nagele, et al. 2016
page 70
closed circuit:
Battery
insulator: does NOT allow electricity to pass through
EXAMPLE: cloth
conductor: DOES allow electricity to pass through
EXAMPLE: wire
Resources
NDT Resource Center – website with great graphics and easy to understand
explanation of circuits, insulators, conductors, etc.:
http://www.ndt-ed.org/EducationResources/educationresource.htm
Energy Quest – an easy to understand informational website with wonderful
graphics on all topics related to energy. Student friendly.
Energy Story – another good website that explores energy and electricity:
http://www.energyquest.ca.gov/story/chapter02.html
Materials
For each student team (if possible would be best to have 35 sets of materials so
each student could build their own circuit)
1 D-cell battery
3 strands of black wire (stripped ends) or alligator connector wires
Mini light bulb
1 set of supplies for a circuit board or factory made circuit board
2” X 4” Piece of cardboard
Light bulb holder
Battery holder
2 brass fasteners
Large paper clip
1 rubber band
1 wood tooth pick
1 strip of aluminum foil
Household light switch & 2 alligator connector wires
Science journals and pencils
LESSON 6 Current Electricity – Circuits and Switches
Nagele, et al. 2016
page 71
For the class
Overhead 1: Definitions
Overhead 2: Write in your Science Notebook
Overheads 3 & 6: Light The Bulb/Add A Switch and Insulators and Conductors
Overhead 5: Diagram of a Light Switch
Overhead 4: Electrical Symbols
http://www.rapidtables.com/electric/Electronic_components.htm
Preparation
Lay out supplies needed for team experiments. Make arrangements for classroom
Career Exploration presenter.
Time
60 minutes
Procedure
PART 1: Making a Closed Circuit With a Light Bulb
1. Explain to students that electricity travels in loops, called a closed circuit
(from the word “circle”). It must have a complete path from the power source
such as the chemical energy in batteries through the wires and back to the
battery. The opposite of a closed circuit is an open circuit where the pathway
for electrons to flow has a break or open space. Electricity (moving electrons)
cannot flow in an open circuit. Show student overhead 1.
2.
a. Tell students that they are going to make an actual closed circuit that will
power a light bulb by using the stored (potential) chemical energy in a
battery to produce electricity.
b. Using Overhead 2: “Write in Your Science Notebook,” discuss the
following while students write in their science notebooks.
For electricity (for electrons to flow) you need:
• Complete loop or circle (closed circuit) formed by a conductor, we will
use wire;
• Electrical source: we will use a battery. The electrons move along a
path only when they are part of a closed circuit. Batteries convert
stored chemical energy into electrical energy (more detail about how
a battery works is provided in Lesson 9);
• A load: we will use a light bulb. A load is the item you want to power.
LESSON 6 Current Electricity – Circuits and Switches
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page 72
c. Give each team (or each student) the following items: 1 battery holder
with switch and light bulb holder, 1 D battery, 1 mini light bulb, 3 black
wires, a piece of cardboard and tape.
d. Remind the students that electricity will only flow through certain
materials called conductors (materials that can conduct electricity) such as
metals and metal wire.
e. Before they begin, ask them to draw in their notebooks a design for a
closed circuit that will use electricity to light the bulb using the materials
provided. Have them draw their design and label the parts (list the parts
on the board: battery, wire, bulb, bulb holder, battery holder, and
battery). Tell them that you or an adult volunteer must check their
drawing before they begin to build their circuits.
f. Explain that engineers go through a process of thinking, drawing their
plans, building from their plans, and then testing what they built. If what
they build (in this case a closed circuit) doesn’t work, they go back to the
drawing board and repeat the process until they get it to work.
g. Once students have a design written in their notebooks, have them create
a circuit with the materials you’ve given them, and test it. If it doesn’t
work help them think through what they might change, and start again as
an engineer would do, by reworking their drawing/design before building
and testing again.
h. You might ask them to draw with arrows the path they believe the
electrons/electricity will take. Be sure the drawing represents a complete
circuit showing electrons going not only to the bulb, but also back to the
battery. Overhead 3 of 6 (Trial 1) may be used to help students further
investigate their circuits.
i.
Have a couple of groups of students share their designs and lessons
learned with the class.
Note: To work, students should: place the battery in the battery holder;
attach one wire to each terminal of the battery; and connect the loose
ends of the wires to the light bulb holder (see diagram).
LESSON 6 Current Electricity – Circuits and Switches
Nagele, et al. 2016
page 73
"Circuit Sense." 4-H Electric Series.
Vol. 1. [Washington, D.C.]: National
4-H Cooperative Curriculum System,
2002. 3. Print.
Simple circuit without switch.
j.
Now introduce students to the electronic symbols that electricians and
engineers use to represent the different parts of a circuit. Use Overhead 4
or use this as an overhead to show symbols.
http://www.rapidtables.com/electric/electrical_symbols.htm.
Ask students to draw their closed circuit using these symbols next to or
below their hand drawing. Sample:
LESSON 6 Current Electricity – Circuits and Switches
Nagele, et al. 2016
page 74
PART 2: Switches: Control the Flow
1.
Explain to students that they can actually control the flow of electricity
through the use of switches to open and close their circuit, thus “switching”
the load (light bulbs) “on” and “off.”
a. Ask students to name ways they use switches every day to control the
flow of electricity, turn it on or off, to electrical devices in their home and
school. When we flip on a light switch, we close a circuit. The electricity
flows from a power plant (instead of a battery), through the power lines
to the house or school electrical wires, through the light cord, through the
light bulb and back again to power plant. When we flip the switch off, we
open the circuit. No electricity flows to the light bulb. Demonstrate using
a table lamp and light bulbs for students to observe.
b. Give each team of students a large paper clip, 2 brass fasteners, and
another wire or alligator connecting wire. Ask students if they can figure
out how to use these items to create a switch in their circuits. Facilitate
teams’ success as shown in diagram below.
Note if using a factory made circuit board, the metal bar acts as a switch.
Have students test their switch by opening and closing their circuit.
NOTE:
Alligator connecting wires
can be used in this activity
in place of the wires
shown in these
illustrations.
Set up with circuit board and switch.
LESSON 6 Current Electricity – Circuits and Switches
Nagele, et al. 2016
page 75
Alternative set up with switch.
c. Using Overhead # 5, explain how the light switch on the wall of the
classroom works. Pass out wall household light switches and demonstrate
how the switch opens and closes a circuit to turn the lights on and off, by
disrupting the flow of electrons (electricity). Ask students why switches
are important to us.
d. Have them look at their circuit designs and incorporate a household light
switch to their drawings and label it.
e. Have students build and test the household switch in their circuit.
Note: Handout 3 of 6 (Trial 2) can be used to facilitate Parts 2 and 3.
PART 3: Insulators and Conductors
1. Collect the household switches and distribute toothpicks, rubber bands, and
aluminum foil to teams.
Career
Exploration
2.
Ask student to define conductors and insulators as related to electricity. Have
student copy definitions in their notebooks from overhead #1.
3.
Have teams identify materials that are insulators and conductors of
electricity using the items you distributed as switches in their circuits.
Students can try other materials from the classroom as well. See overhead #6.
If an engineer or college engineering student is available have them explain the
process of engineer design to the class and give a real life example/demonstration
in their field of engineering. You might also have them share with students all of
the different fields that employ engineers.
LESSON 6 Current Electricity – Circuits and Switches
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Assessment
Grade designs of circuit drawings.
LESSON 6 Current Electricity – Circuits and Switches
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RESOURCES:
Short Videos that demonstrate energy
Draw a circuit board that works! A new technology. Circuit scribe
When dreaming up that world-changing invention, wouldn't it be great if you could just sketch
out the circuits and have them magically work? That's the idea behind Circuit Scribe, a ballpoint
pen that's full of quick-drying ink that'll help you doodle your circuits on notebook paper.
Emerging out of research from the University of Illinois, the team is now accepting your cash
through Kickstarter to help bring it into the real world. $20 will get you a pen and an LED
component, while $30 will buy you a basic kit, complete with plenty of accessories to help you
test the systems to their fullest. We imagine it'll be a big hit with STEM educators as well as
hobbyists, but if you're not yet convinced, check out the video to watch it in action.
http://www.engadget.com/2013/11/21/circuit-scribe-kickstarter/
All about symbols and electricity
http://www.electronic-symbols.com/index.htm
Electrical Symbols & Electronic Symbols
Electrical symbols and electronic circuit symbols are used for drawing schematic diagram. The
symbols represent electrical and electronic components. And definitions!
http://www.rapidtables.com/electric/electrical_symbols.htm
INTERACTIVE
Teaching about circuit boards….all types of circuit boards and interactive lessons to explore.
http://www.teachengineering.org/googlesearch_results.php
EXTENSION ACTIVITIES
Students Illuminate Their Ideas with Paper Circuitry—poetry and circuitry
http://www.middleweb.com/15344/students-illuminate-ideas-paper-circuitry/
Printed circuit boards—next steps. Making your own flashlight
http://video.mit.edu/watch/how-to-make-your-own-circuit-board-24537/
For the real Geeks and those who are just interested in DIY.
I want to share my personal experience with heat toner transfer method of making PCB.
It's easy to learn for beginners and it delivers very good result for fair price.
Do fast prototyping with fun! 8:33min
http://www.instructables.com/id/DIY-Printed-circuit-board/
FIELD TRIP/Careers
Occupational Outlook Handbook and an example of kinds of information your students can find
in exploring careers.
LESSON 6 Current Electricity – Circuits and Switches
Nagele, et al. 2016
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http://www.bls.gov/ooh/installation-maintenance-and-repair/electrical-and-electronicsinstallers-and-repairers.htm
What Electrical and Electronics Installers and Repairers Do
Electrical and electronics installers and repairers install, repair, or replace a variety of electrical
equipment in telecommunications, transportation, utilities, and other industries.
Work Environment
Many electrical and electronics installers and repairers work in factories, which can be noisy
and sometimes warm. Installers and repairers may have to lift heavy equipment and work in
awkward positions. The vast majority work full time.
How to Become an Electrical or Electronics Installer and Repairer
Most electrical and electronics installers and repairers obtain specialized training at a technical
college. Gaining voluntary certification is common and can be useful in getting a job.
Pay
The median annual wage for electrical and electronics installers and repairers was $51,220 in
May 2012.
Job Outlook
Overall employment for electrical and electronics installers and repairers is projected to show
little or no change from 2012 to 2022. However, growth rates will vary by specialty. Job
opportunities should be excellent for qualified workers with an associate’s degree in electronics
along with certification.
Similar Occupations
Compare the job duties, education, job growth, and pay of electrical and electronics installers
and repairers with similar occupations.
More Information, Including Links to O*NET
Learn more about electrical and electronics installers and repairers by visiting additional
resources, including O*NET, a source on key characteristics of workers and occupations.
National Career Development Association
These links include many resources, services, and tools which assist users in exploring careers,
planning for the future, searching for employment, and finding the additional training necessary
to pursue a dream. Most of these resources are free, and several were developed in countries
other than the United States. This is a mere sample of what is available online, but it can serve
as a starting point for career counselors or for career-seekers.
http://www.ncda.org/aws/NCDA/pt/sp/resources
Resource page for students and teachers about careers
http://www.bls.gov/k12/students.htm
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