Students will be introduced to the concept
of electricity by watching a short video with a catchy tune that will
have them looking for similar examples of electricity right in the
classroom. Extend this activity to walking through the school and
noting all the uses of electricity. For homework, ask students to
make a list when they go home. Several fun activities engage students
to consider what is meant by an electric circuit and how electrons
flow through wire as either open or closed circuits. Then students
will have the opportunity to explore how a flashlight works by taking
it apart and drawing the components and then lighting the bulb and
putting it back together. Through this activity, students will
experiment with lighting bulbs and learn the difference between
simple series and parallel circuits.
Part 1: What Is Electricity and What Is
Meant by Open and Closed Circuits?
Review what students know about electricity
as a form of energy from previous lessons (i.e., Where do we get it
from? Is it kinetic energy? It is potential, or stored, energy like
batteries? How do we use it?).
Turn on various electrical devices in the
classroom (CD player, light, TV, etc.) Ask students to give other
examples of electricity they see in the classroom or in their homes
and how the devices are able to work. Once students give “energy”
as the answer, ask them to define it. Energy is defined as the
ability to do work or make a change.
If time allows, take a walk through the
school and write down all the appliances, devices, machines, etc.
that use electricity.
Have students stand in a circle, close
enough to pass items from one student to the next but far enough
apart that just their hands touch. Give each student a ball (e.g., a
tennis ball). Explain to students that they have to pass the balls
from one person to the next with each person only holding one ball at
a time. Give students time to complete the task.
Remove one student from the circle and ask
students to pass the balls as before. They should not be able to
complete the task due to the open space. Collect balls and have
students remain in the circle.
Ask students to use different words to
describe the two different scenarios. Make a list on the board and be
sure that “open” and “closed” appear on the list.
Now tell students they are going to pretend
their arms are the wires that carry electricity. Have them touch
palms to complete the circle.
Ask two students next to each other to stop
touching each other and ask students if the current is open or
closed. Now have the two students each hold one end of a metal strip.
Now ask if the current is open or closed.
Explain that the metal strip is a conductor
and as long as each student is touching the metal “switch,”
electricity can flow. If the switch is turned off, by one student
letting go of the metal strip, the current will stop or is open so
that electricity cannot continue to flow.
Wrap up the activity by explaining open and
closed circuits and emphasizing two things that are needed: a power
source and a complete circuit. Explain to students that wires in a
circuit that connect objects (like switches, light bulbs, buzzers,
etc.) must start and end at the power source before they can work.
That’s why batteries have a top and bottom (+ and −) so they can
carry the charge all the way around.
Part 2: How Do I Light a Bulb?
Before starting this activity, ask students
what they would purchase if they were asked to go to the store and
buy a pound of electricity. Ask them to think for a minute and then
share their answer with their partner. Then ask for volunteers to
write their answer on the board. If they answer “light bulbs,”
ask if that means light bulbs are electricity. Or is it to say that
light bulbs work using electricity? This is a good opportunity to
correct misconceptions about electricity and reinforce the concept
that electricity is not matter. You cannot hold it in your hand
because it is a form of energy and does not have mass or volume like
matter.
Break students into pairs and give them a
flashlight. Ask if any of them have ever opened a flashlight before.
Ask students to take the flashlights apart and take the inside parts
out (spring, battery, bulb). Caution them about the breakable parts
and to hold the flashlights over their desks in case these parts fall
out. Have students draw and label the parts of the flashlight in
their journals.
Without giving directions, ask students to
light the bulb with only the parts that they removed from the battery
casing. To ensure success and lessen frustration, the teacher can
strip the ends of the wire with a wire stripper. Provide assistance
as needed. Ask students why they think removing the plastic coating
from the wire is important to solving the problem of lighting the
bulb. Ask students to experiment and raise their hands once they
light the flashlight. Instruct students to keep secret for the moment
how they were able to light the flashlight. Instead have students
draw a picture of what they did in their science journals while the
other students complete the task.
Allow students to visit with other groups
and try several ways to get the bulb to light. Ask students to draw
ways that work and ways that do not work. Now ask students to use
both batteries and the wire to light the bulb. It may be tricky but
they will notice the bulb is much brighter now. Have students
reassemble the flashlights and turn them on. Compare the brightness
of the bulb now with the brightness when they lit the bulb outside
the flashlight with the same two batteries. They should find them to
be identical. Ask students to write in their journal what they have
discovered, or any rules they established about getting a bulb to
light.
Discuss as a class how to light a bulb and
explain why it must be a closed circuit. Explain when you flip on a
light switch, you are actually closing or completing the circuit. A
circuit is the path that electricity flows. When you flip the light
switch off, you are opening the current and the light turns off
because the electrons cannot flow.
Ask students to show their drawings of their
completed circuit. Are they alike or different? To simplify drawing
circuits, there are common symbols to illustrate each part. Show
students the symbols for drawing circuits. Hand out the Electrical
Symbols Chart (S-4-5-3_Electrical Symbols Chart.doc) to each student. Using the symbols for batteries, wire, and a
bulb, draw a simple circuit based on what students just did to light
the bulb.
Now pass out switches and bulb holders to
each pair of students and have them light the bulb using the switch.
Take a moment and compare these materials to the ones they used to
light the bulb in the flashlight. Now draw the simple circuit using
these two new symbols. Ask a student to draw it on the board or
overhead projector. Have students check their work.
Wrap up the activity for the day by
reviewing what is necessary for a light to work in a house or
classroom. Ask students to think about if and how the simple circuits
can handle more than one light at the same time.
Part 3: What is a Simple and a Parallel
Circuit?
Review the activity from Part 2. Discuss
with students what one must have to light a bulb and a simple
circuit. Ask them how many bulbs they were able to light in the
previous activity. Now challenge them to see how many bulbs they can
get to light using their knowledge of circuits from the previous
activity.. Have students draw their setup once they light as many
bulbs as they can. Who could light the most bulbs at one time on the
same circuit? After applauding their efforts, ask them to draw the
setup and label the parts using the new symbols. Ask students how
they should label the pathways connecting the batteries, wires, and
bulbs. When they say “circuit,” write it on the board and define
it as a complete pathway from one end of the battery through the wire
and bulbs to the other end of the battery and through the battery
again. “This is that continuous pathway for the tiny charged
particles called electrons that flow through the wire and carry the
electric current.” Sketch together the circuit students
constructed and label the parts. Students should have the same in
their journals.
Example of a sketch with information:
The battery pushes electrons from the
negative terminal (where there are many electrons), through the
switch, the light bulb, and the wire into the positive terminal
(where there are not many electrons). As electrons pass through the
wire and into the light bulb, a special kind of wire inside the bulb,
called a filament, lights the bulb.
The circuit has been broken. The light bulb
is not lit. The flow of electrons has stopped because there is a gap
in the circuit, and the electrons no longer have a closed path.
Discuss as a class how many bulbs were lit
on one circuit. What did students notice about the light bulbs? (The
more you add, the less bright they become.) “Why is this?” (Each
bulb draws on the energy source and they become dimmer and weaker.)
“There are two basic ways in which to connect more than two
objects that use electricity: series and parallel.”
A series circuit has only one path for
electrons to flow. Components are end to end in a line forming a
single path. Ask students if they have put lights on a tree, and when
they plugged in the lights, the lights didn’t work. If one bulb
goes out, they all go out. This is one of the disadvantages of series
circuits.
A parallel circuit may have multiple light
bulbs because it has more than one continuous path for electrons to
flow. Each individual path is called a branch. All components in
parallel circuits connect between the same set of electronically
common parts, or in other words they are connected across each
other’s loads.
Have students work in pairs and try to build
a parallel circuit. How many paths and bulbs can they wire with one
battery? Have students draw their parallel circuits and demonstrate
them to the class. Discuss the results and use the Series and
Parallel Circuits handout (S-4-5-3_ Series and Parallel Circuits.doc) as a reference.
Series Circuits
A series circuit allows electrons to follow
only one path. All of the electricity follows path #1. The loads in a
series circuit must share the available voltage. In other words, each
load in a series circuit will use up some portion of the voltage,
leaving less for the next load in the circuit. This means that the
light, heat, or sound given off by the device will be reduced.
Parallel Circuits
In parallel circuits, the electric current
can follow more than one path to return to the source, so it splits
up among all the available paths. In the diagram, some current
follows path #1, while the remainder splits off from #1 and follows
path #2. Across all the paths in a parallel circuit the voltage is
the same, so each device will produce its full output.
- Extension: