Download Parallel and Series Circuits

Parallel and Series Circuits
Gabriel Alsina
Rationale:
This lesson will introduce students to series and parallel circuits and should follow
lessons introducing circuit building in general. This lesson helps students understand more about
how electricity works while keeping it all grounded and connected to real circuitry. It all also
satisfies the following Wyoming State Science Standards:
SC11.1.13
SC11.2.4
SC11.2.5
SC11.3.2
Energy and Matter: Demonstrate an understanding of types of energy, energy
transfer and transformations, and the relationship between mass and energy.
Students investigate the relationships between science and technology and the role
of technological design in meeting human needs.
Students properly use appropriate scientific and safety equipment, recognize
hazards and safety symbols, and observe standard safety procedures.
Students examine how scientific information is used to make decisions.
• Interdisciplinary connections of the sciences and connections to other subject
areas and career opportunities.
• The role of science in solving personal, local, national, and global problems.
Objectives:
This lesson will give students an opportunity to use their scientific inquiry abilities while
learning more about electricity and circuits. Each student will have an opportunity to construct
several circuits and measure the voltage and currents present in these circuits. Students will learn
how to build simple circuits by looking at circuit diagrams and get more practice in measuring
voltage and current using a multimeter. Emphasis will be placed on series and parallel circuitry
and their properties. Students will also learn how to troubleshoot circuits.
Materials:
Multimeters
Breadboards with voltage source
Required LEDs
Pre-cut and stripped wires
Lab worksheets
Troubleshooting tips page
Statement of Engagement:
Students will begin this lesson by playing around with circuit simulation software
available at http://phet.colorado.edu/en/simulation/circuit-construction-kit-dc. Their task will be
to light up 3 light bulbs with only 2 batteries. This should give them a fun way to start interacting
with the circuits. Many of them will probably gravitate towards a series circuit although a few
parallel circuits might also be produced. The teacher should then use these student produced
circuits as a launching point for the day’s lesson.
Minute by Minute Breakdown:
Time (min)
10 - 15
8 - 10
5
5
25 – 30
8 -10
13 - 15
What the teacher is doing
Start students on circuit simulation with
the task described above. Facilitate when
necessary.
Use student constructed circuits to
illustrate differences between series and
parallel circuits.
Give a brief introduction to circuit
troubleshooting using the circuit
simulation software. Ask students how
they would proceed when a light wouldn’t
come on in their circuits.
Introduce today’s lab. Hand out materials
and worksheets. Group students.
Answer questions and ensure students are
on task and working through the labs.
Once finished, have the students answer
any remaining questions on their
worksheets and clean up their work areas.
Discuss results with the entire class. Ask
class what the main differences between
series and parallel are. Have students
share any troubleshooting stories.
What the student is doing
Experiment with components and try to
accomplish task.
Presenting their circuits. Listening and
asking questions.
Listening and proposing possible
solutions to encountered problems.
Listening and following instructions.
Working on labs.
Finish worksheets and clean up.
Participate in discussion, ask questions.
Troubleshooting Tips
If a problem arises with the lab here are some things to try:
1. Start simple
a. Is it wired correctly?
b. Are all the connections good or is one loose?
c. Is the potentiometer turned all the way to one side or another (if connected)? If so
this may be adding too much resistance to the circuit so try turning it the other
way.
d. Is there enough light? Solar panels are very picky about the amount of light they
need. The more the better. Lab 2: Task 1 actually experiments with shading part
of the panel.
2. Swap identical components and check to see if it fixes the problem. If it does, discard the
replaced component.
3. Remove any parallel components to see if the circuit will begin working.
4. Divide the circuit into smaller systems and test each individually.
Lab #1: Circuit Introduction
NOTE: To measure voltage you must measure it across the LED or voltage source. To
measure current you must connect the ammeter in series with the circuit.
Task 1: Parallel Circuits
1) Connect the circuit shown in figure 1. This connects the LED’s in parallel. See
how they are on opposite sides of the box the wires make.
Figure 1
Green
Yellow
Voltage Source
2) Take measurements after the circuit above is constructed. ‘I’ stands for current
and ‘V’ for voltage.
Measurements:
Vsource
Isource
Igreen LED
Iyellow LED
Igreen + Iyellow
3) Does Igreen + Iyellow equal the current out of the voltage source? Why?
4) Disconnect one LED, does the other LED turn off? Why?
5) Reverse the wires going from the voltage source to the LEDs. What happens?
Why?
Task 2: Series Circuits
1) Connect the circuit as shown in figure 2. Notice how the wires make a
continuous loop, this is known as a series connection.
Figure 2
Yellow
Green
Voltage Source
2) Take the following voltage measurements after the circuit above is constructed.
Measurements:
Vgreen
Vyellow
Vsource
Vgreen + Vyellow
3) Does Vgreen + Vyellow = Vsource? Why?
4) Take the following current measurements after the circuit above is constructed.
Measurements:
Ivoltage source
Ibetween LEDs
5) Are the two currents equal? Why?
6) Disconnect one LED, does the other LED turn off? Why?
Task 3: Series with a Variable Resistor
1) Connect the circuit as shown in figure 3. This is also a series connection; we just
added a variable resistor, called a potentiometer (Pot).
Figure 3
Green
Yellow
Pot
10k 40%
Voltage Source
2) Try turning the potentiometer. What happens? Why do you think this happens?
3) Is the resistance in the potentiometer higher or lower when the lights are dimmed
versus full brightness?
4) As the extra resistance is added does the current in the circuit increase or
decrease?
5) With the LED’s dimmed, take the following measurements.
Vpotentiometer
Vgreen
Vyellow
Vsource
6) Add Vpotentiometer + Vgreen + Vyellow. Is it equal to Vsource? Why or why not?