Transcript Powerpoint - Cockeysville Middle

ELECTROMAGNETS
Objective: To explore electric circuits in
order to explain how they relate
to magnetic fields.
Energy Note: Are electricity and magnetism related ?
Drill:
1. Get a new lab from the SET.
2. Read Activity
3. Imagine completing the activity
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Activity 1: Exploring a Compass
1. Take the magnet and the compass.
2. Hold them about 30 cm apart.
3. Slowly move the compass closer to
the magnet.
4. Record your observations. Repeat if
necessary.
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1. Construct a simple circuit using the
provided materials. (Just a cell wired to a
switch) Leave the switch open.
2. Place the compass near the circuit.
Record your observations in the left half of
Figure 1, “Compass Observations.” (Draw
the compass needle.)
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3.Close the switch. Record your
observations in the right half of
Figure 1, “Compass Observations.”
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Explain the movement of the compass needle after
the wire was connected to the circuit. Use your
observations and prior knowledge about the
effects of magnets on compass needles to
support your answer.
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Compasses react to magnetic fields.
The compass needle moved when the
circuit was closed.
Therefore, the circuit must produce a
magnetic field.
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The observations you just made
represent one of the biggest blunders
in the history of science. However, this
blunder has revolutionized technology
and enabled scientists to develop
devices that convert electrical energy
into mechanical energy.
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DAY 2
Objective: To explore electric circuits in
order to explain how they relate
to magnetic fields.
Energy Note: Are electricity and magnetism related ?
Drill:
1. Take out both your lab and yesterday’s
Lesson Sheet.
2. Wait for directions.
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READ and NOTATE the
passage, “OERSTED’S
SURPRISE”.
What problem did Hans Oersted
have?
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Why does a compass needle move
when it is placed next to an electrical
circuit? Use information from the
reading to support your response.
A compass needle moves when
placed next to an electrical circuit,
because an electrical circuit
PRODUCES A MAGNETIC FIELD.
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Homework:
Electromagnets Lab – Pre-reading
and Hypothesis
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Problem Question:
How does the number of coils of wire
wrapped around a core affect the strength
of the electromagnet?
Independent Variable: # of coils wrapped
around the core.
Dependent Variable: strength of the
electromagnet.
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Materials:
iron nail
electrical wire (1 m)
Switch
paper clips (1 box)
two alligator wires 2 D-cells w/ holders
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Hypothesis:
(Write in “If…,then…, because…” format.)
If the number of coils wrapped around
the core increases,
Then the strength of the electromagnet
will…,
because…
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1. Strip the plastic covering from the two ends of the wire.
(This may already be done for you.)
2. Make ten tight wraps around the middle of the nail,
starting about 5 centimeters from the end of the wire.
3. Place the D cells in the battery holders. Connect the
cells together with a wire.
4. Attach one open terminal of a cell with a wire to a
switch. Leave the switch open.
5. Attach one end of the wire to the switch and the other
end of the wire to open terminal of the second cell.
6. Close the switch to operate.
Caution: Do not leave the switch closed for more than
fifteen seconds at a time. The wires may become very hot.
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DAY 3
Objective: To perform an experiment in
order to determine how the number of
coils wrapped around an iron core
affects the strength of an electromagnet.
Energy Note: How can the strength of an electromagnet be
increased?
Drill: 1. Take out you lab, your log, and your ZIP
Sheet.
2. Move into your groups.
3. Build a 20 coil electromagnet.
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1. Place the paper clips in a small pile on the table.
2. Complete the circuit containing the electromagnet by
closing the switch.
3. Place the tip of the electromagnet slowly into the pile of
paper clips.
4. Remove the electromagnet from the pile.
5. Open the switch. Count the number of paper clips that
adhered to the end of the electromagnet.
6. Record the data in the appropriate space in Chart 1,
“Effect of the Number of Coils on Number of Paper
Clips Lifted by the Electromagnet.”
7. Repeat steps A-F using electromagnets constructed
with 20, 35, and 50 coils.
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CHART 1
EFFECT OF THE NUMBER OF COILS
ON THE NUMBER OF PAPER CLIPS LIFTED BY THE
ELECTROMAGNET
Number of Coils
Number of paper
Clips Lifted
10
20
35
50
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Conclusion
Answer the lab question. Provide
evidence from the lab to support
your conclusion.
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RECAP and DEMO
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Homework:
Lab Analysis
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