Download Chapter 6: Electricity for Everyone

Chapter 6: Electricity for Everyone
Overall:
The chapter challenge for this section can be easily related to real life physics. A great
introduction to this unit is to watch videos about people who don’t have homes and easy
access to electricity. Habitat for Humanity has some great videos describing what they
do, that emphasize how others live. This link to humanity has a great effect on the
students.
Scientific Practices: It is important to recognize that scientific practices are a key part
of the investigative process in this book even though they are not always specifically
drawn out in a manner you may be used to. Your students will be responsible for
understanding experimental design and must be able to create hypotheses, identify
variables and constants, interpret qualitative and quantitative data, and make
conclusions that justify what has been learned. Ensure that your instruction explicitly
focuses on these practices in all the sections you teach. You can expect that district
and state assessments will contain questions relating to scientific practices
Learning Outcomes, Pitfalls, Misconceptions, Notes by Section
Section 1: Generating Electricity
learning outcomes:
Trace energy transformations through a circuit.
Create a frame for electricity.
Create a circuit that lights a bulb.
Use a hand generator to explore the relationship between input energy (crank speed)
and output energy (brightness).
pitfalls:
The light bulbs can be very easy to burn out with the hand generator. It can be helpful
to have students set up all circuits with a second bulb in series so that they are harder
to burn out. If you do this, it is important to make sure the kids are making their
observations of one bulb and not comparing the two bulbs, which will be done later in
the chapter.
An alternative to the 2nd bulb in series is a lot of discussion about proper generator use
or a number of back up bulbs for burn outs. Extra bulbs on hand are encouraged
regardless of the method you use.
Cranks can be damaged with misuse. Give students guidance before allowing them to
play with the cranks.
Students are likely to be in different stages of understanding about circuits. To speed
things up, tell them how to set the circuit up. With more time, students get a better
understanding of the circuits by exploring on their own and finding out how to set up the
circuit.
misconceptions:
Students are likely to have an understanding of negative and positive and a directional flow of
electricity. They should find out that the wires will work regardless of color and placement in this
case. It is important that they determine the minimum requirements to a successful circuit and
that they realize why each part is important.
notes:
There is some good information in the teacher’s edition background section about electricity use
around the world. Sharing some of this may increase student interest.
Section 2: Modeling Electricity: The Electron Shuffle
learning outcomes:
Create a physical model for electric current and potential energy.
Use the model to follow the flow of electric charges through a series circuit.
pitfalls:
This section will be much more successful with teacher preparation beforehand. It is
helpful to create signs to identify the student roles in the circuit (for example, the battery
would have a necklace or taped on sign to indicate that he/she is the battery). It is also
helpful for the statements that each person makes to be written down for students so
they will know what to say when walking through the circuit.
Provide notes for students to either receive or copy down about the vocabulary used
throughout the section. Without encouraging students to write this down, they may
struggle to remember the new important terms.
Create a table to organize variables, symbols, and units. This will be helpful to your
students for keeping these terms straight.
Make the models as a class, but allow students to try out changes to the Electron
Shuffle on their own in their notebooks.
misconceptions:
Students don’t look at the circuit as a whole, but instead look at each piece
independently. They need to see the bigger picture.
The electrons do not light up the bulb – the students should recognize that the electrons
continue through the circuit and don’t stop at the bulb.
Make sure students see the difference between voltage and current. The battery does
not supply the current, but rather the voltage.
Students may miss that the bulbs pull the current from the battery, and therefore
determine how much current is flowing to them. They do not, however, determine the
total flow through the circuit.
notes: This is a great model for getting students a beginning understanding of series
circuits. You will build both series and parallel circuits at the end of section 3. Make sure
that students recognize that everything they have learned at the end of this section relates
to series circuits and that parallel circuits (which you learn about next) will work differently.
Section 3: Series and Parallel Circuits
learning outcomes:
Compare series and parallel circuits
Discover output limit of generator
Continue showing the importance of modeling in science
pitfalls:
The output limit portion of this lesson can be lost if you do not pull it out.
Again, you have to work to make sure you are not burning out light bulbs. Be cautious
with the generators and have back-up bulbs.
Make sure to emphasize what you are learning while modeling the electron shuffle. It is
important that students are seeing the difference between the series and parallel circuit.
Since they have already modeled a circuit this way, it easy to stop paying attention to
detail.
misconceptions:
Many students observed bulbs in the parallel circuit getting dimmer when more bulbs
were added. Be sure they are not putting their preconceived notions into their results.
notes:
Section 4: Ohm’s Law- Putting up a Resistance
learning outcomes:
Calculate resistance when given the voltage drop and current.
Construct a series circuit.
Use an ammeter and voltmeter in a series circuit.
Using a graph, relate current, voltage, and resistance as shown in Ohm’s Law.
pitfalls:
Teacher needs to make the black box resistor. Not provided with the kit or textbook
supplies.
misconceptions:
Students often think that they can manipulate the current in a circuit. It is useful to use
the formula I = V/R, to show that the voltage and resistance control the current.
notes:
This is a good time to do some calculation practice with Ohm’s Law.
Section 5: Electric Power: Load Limit
learning outcomes:
Define power, insulator, and conductor.
Correctly use the formula P = IV.
Determine the power limit of a 120 volt circuit.
Differentiate between fuses and circuit breakers. Understand what those items
do and why they are necessary.
pitfalls:
After warning students not to over crank the generators earlier in the chapter, they are
very hesitant to crank the generator enough to burst the balloon. They will need some
encouragement to really crank the generator.
Taping the steel wool onto the balloon can be challenging. It may be easier to tape the
clips to the balloon and clip the steel wool in between.
misconceptions:
The word fuse is often over used in our society. It is important to clearly differentiate
between fuses and circuit breakers and discuss which item is used in which situation.
notes: