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| WV State Standards: |
| Science:
SC.8.4.18, SC.9.4.18, AES.4.34, AP.4.19 |
Technology:
TEC
9-12.1.2, TEC 9-12.2.1, TEC 9-12.2.2, TEC
9-12.3.2, TEC 9-12.5.1, TEC 9-12.5.2
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| National Standards: |
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| Blooms Taxonomy:
Knowledge,
Comprehension, Analysis, Synthesis |
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21st Century Skills:
Creativity and Intellectual Curiosity,
Information and Media Literacy,
Self-Direction |
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Description:
To introduce this lab, the teacher will use a
demonstration of how the length of a wire influences the resistance
of the wire. In the lab, students will conduct
heat through three metals (copper, aluminum, and iron) to see if the
density of a metal influences its resistance to the flow of energy.
Through the use of Excel graphing and finding the slope of the line,
students will predict the conductivity of gold and silver. Ohm's
Law will be taught using an electrical circuit composted of a light
bulb, wires, an ammeter, and a voltmeter. Students will calculate
resistance using the equation R = I/V. They will also experiment
with the length of the wire and how it affects resistance. The
purpose is for students to discover which metal they should use to make the wire
that will run from the generator on EdVenture Island. Students will also need to decide where
to position their generator on the island.
Objective(s):
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Students will
associate the density of a metal to its ability to conduct heat and
electricity.
Time Required:
One 45 minute class
period
Pre-Requisite Skills:
Students should
have a basic knowledge of what electricity (static and non
static) is and how a generator produces electricity. Computer
knowledge of Excel is recommended.
21st Century Tools (Technology Tools)
- computer
access per group
- Internet
access
- calculator
(calculations can be done in Excel instead)
- Excel
- projector
(helpful but optional)
- CBL with
conductivity tester (optional)
Instructional Materials
Introduction
Motivation/Context:
In the last
unit students decided as a class which renewable resource they
would use for EdVenture Island. They must now decide where to
locate the new power plant on the island and figure out from the
ores present on the island which metal to make their wire out
of. A demonstration and experiment of how the length and
thickness of a wire influences the flow of electricity, and a lab on
the density of metals and resistance to flow gives students some
ideas as to the variables that must be considered in this decision.
This lesson addresses principles of conductivity, resistance,
and Ohm's Law.
Procedure:
- Review the power source the
class decided they would use on EdVenture Island. Explain
that the students are now working as electrical, civil, and
mechanical engineers deciding where to build the power plant
and how to distribute the power to the homes and businesses on
the island. To do this they must first understand the
principles behind the flow of electricity - resistance.
- Take out the pre-made
demo of the length of wire and the
resistance to flow. Show students that as you or they slide the
alligator clip closer to the bulb that this shortens the path of
resistance and the bulb gets brighter. As you move the
alligator clip away from the bulb this lengthens the path and
the bulb gets dimmer
- Have students access the
Density and Resistance Lab.
Caution them about wearing proper safety equipment, how to
strike a match safely, and how to handle the hot metal safely.
- Have them open Excel and
construct a table similar to the one on the web page.
- Make sure they start timing
when they place the wire in the flame of the candle. Have them
hold it steady using the beaker tongs at the juncture of all of
the metals and not on only one of the wires.
- They will make graphs of
density vs time to fall in part one and density vs. resistance
in part two. They should see that as density increases so does
conductivity, which means resistance is reduced.
- (optional) In part 2 as they
graph in Excel, they could write a formula (i.e. in cell F2 type
=D2/E2, D = voltage and E = current) for the resistance in the
cell and copy that to the column instead of calculating with a
calculator. However if you make them use the calculator they get
more practice with the formula R = V/I.
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metal |
density (g/cm^3) |
time to fall (sec) |
voltage |
current |
resistance |
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aluminum |
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=D2/E2 |
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copper |
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=D3/E3 |
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iron |
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=D4/E4 |
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silver |
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=D5/E5 |
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gold |
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=D6/E6 |
- When they graph, they will
need to data group everything in pink above. This excludes the
density and resistance. See
data grouping instructions.
- Students will need to create
two new spreadsheets in Excel for Part 3. One for the length of
wire and one for the thickness of the wire. Have students use
the apparatus they constructed in part 2 to test the lengths and
thickness of the copper wire. You could have them do the other
metals too at different lengths and thickness if you have
these. A CBL with a conductivity tester can be used, but it is
optional.
- Students will create 4 graphs
for Parts 1, 2, and 3 ( Density vs Time to fall, Density vs
Resistance, Length of wire vs Resistance, Thickness of wire vs
Resistance)
- At the end of class,
have students look at the map of the island and begin planning where
to locate the power plant and discuss the ores that are
available, the cost of extraction, and the cost of use vs
efficiency for conducting electricity. They should understand
that the location should be carefully considered with the
resistance of the material used.
Differentiated Instruction:
Author's Comments:
When determining the
groups, make sure to design the groups so that students with a better
understanding of the lesson might help others in the class.
Be aware of possible power issues within your classroom.
21st Century Assessment/Evaluation:
-
oral discussion
of the demonstration of length of wire and how it affects
resistance
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data collection
and calculations of resistance
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answers to lab
questions in the lab write up
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