19 faraday_s law web

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Student Instruction Sheet 445

FARADAY BUELER S DAY OFFNOT !

Faraday Buelers DayOffNot!

Student Instruction Sheet

Challenge

Investigate the relationship between the magnetic flux, voltage, time, and numberturns in a coil of wire.

Equipment and Materials

Safety PrecautionsRemember, follow the directions for using the equipment.

Background

Michael Faraday discovered that passing a magnet through a coil of wiregenerated a current in the wire. He experimented with the number of loops in thecoil of wire. He also explored how the strength of the magnet affected thevoltage in the coil of wire.

PredictBefore beginning the eLab, complete the prediction portion of the StudentResponse Sheet.

Computer with USB Port 400-Turn Coil

PASPORT USB interface 800-Turn Coil

PASPORT Voltage/Current Sensor Student Instruction Sheet

DataStudio software Student Response Sheet

Alnico Bar Magnet

19. Faraday's Law of Electromagnetic Induction

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446 Student Ins truc tion Sheet


Explore

Computer Setup

1. Plug the PASPORT USB interface intothe computers USB port.

2. Plug the Voltage/Current Sensorinto the USB interface. This willautomatically launch the PASPortalwindow.

3. Choose the appropriate DataStudio configuration file entitled

19 Faradays Law CF.ds

Note: Configuration files automatically launch the appropriate

display(s), sampling rate(s), etc.The Voltage/Current Sensoris a multi-sensor. As itmeasures two distinctlydifferent quantities, you mayfind it challenging to use thesensor properly. Use theinformation at right to guide

you in the use of the Voltage/Current Sensor.

Equipment Setup

1. Set up the equipment as shown in the figure.

2. Connect the red voltage lead of the Voltage/Current Sensor to the labeled side of the 400-Turn Coil. Connect the black lead to the otherterminal. Place the coil in a position where the bar

magnet can easily pass through the hole. (Forexample, place the coil at the edge of a table.)

Note: Do not let the bar magnet hit the flooror any solid object. The magnet is fragile andcould break.

The voltage portion of

the sensor measures

voltage across a part

of a circuit in volts.

The current portionof the sensormeasures currentthrough the circuitin amps.

to the USB link


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Student Instruction Sheet 447


Record Data

Part 1: Compare the 400-Turn Coil to the 800-Turn Coil

1. Hold the magnet so that the south end is about 2 cm above the coil.

Note: If you are using the PASCO Model EM-8620 Alnico BarMagnet the North end is indicated by the narrow groove nearone end.

2. Click the Start ( ) button. Let the magnet drop through the coil.

Data recording will begin when the magnet falls through the coil and thevoltage from the coil reaches 0.05 V. Data recording will end automaticallyafter 0.4 seconds.

3. Replace the 400-Turn Coil with the 800-Turn Coil and perform the sameprocedure above.

4. After collecting data, replace the 800-Turn Coil with the 400-Turn coil.

Part 2: Compare one bar magnet to two bar magnets together

1. Tape two bar magnets together so both north poles are next to each other.

2. Repeat the data recording procedure using the double-strength magnetthrough the 400-Turn Coil.

Analyze

Find the area under the curve of voltage versus time.

1. Click the Scale to Fit ( ) button to rescale the graph.

2. Record the value of Max as the Maximum Voltage for each of the data runsin the data table on the Student Response Sheet.

3. Use the cursor to select a region around the first peak of the voltage plot.The value for Area appears in the legend box in the graph. Record the Area inthe data table of the Student Response Sheet.

4. Perform the same procedure for the second peak and record its Area in thedata table of the Student Response Sheet.


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448 Student Ins truc tion Sheet


5. Perform the analysis for the 800-Turn Coil.

6. Switch to the data run for the double magnet through the 400-Turn Coil andrepeat the analysis.

7. Save your DataStudio file (on the File menu, click Save Activity As...) to thelocation specified by your teacher.

8. Answer the questions and define the vocabulary words on the StudentResponse Sheet.

9. Follow your teachers instructions regarding cleaning up your work space.


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Student Response Sheet 453


Student Response Sheet

Name:__________________________________

Date:_______________________________

Faraday Buelers Day OffNot!

VocabularyUse available resources to find the definitions of the following terms:

electromagnetic induction: _______________________________________

___________________________________________________________

magnetic flux: ________________________________________________

___________________________________________________________

Predict

1. You can send electricity through a conducting wire to make a magnetic field.Do you think the reverse is possible? Do you think you can use a magnet and aconducting wire to make electricity?

___________________________________________________________

___________________________________________________________

2. How do you think the number of loops in a coil of wire affects the voltage ofthe electricity generated in the coil?

___________________________________________________________

___________________________________________________________


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454 Student R esponse Sheet


3. How do you think the strength of a magnet used to generate electricity in acoil affects the amount of voltage in the coil?

___________________________________________________________

___________________________________________________________

___________________________________________________________

Data Table

Analyze

1. How does the graph of the 400-Turn Coil compare to the graph of the 800-Turn Coil?

___________________________________________________________

___________________________________________________________

2. According to Faradays Law, the areas of the two peaks of the voltage-timecurve should be zero when added together. Is this the case for the data yourecorded?

___________________________________________________________

___________________________________________________________

3. How does the graph of the double-magnet compare to the graph for the 400-Turn Coil (with the single magnet)?

___________________________________________________________

___________________________________________________________

Data Run Area: Peak 1 Area: Peak 2 Total Area MaximumVoltage

400-Turn Coil

800-Turn Coil

Double-magnet


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Student Response Sheet 455


Synthesize

1. How does the number of turns in the coil affect the voltage induced?

___________________________________________________________

___________________________________________________________

___________________________________________________________

2. Is the incoming flux (area under first peak) equal to the outgoing flux (areaunder second peak)?

___________________________________________________________

___________________________________________________________

___________________________________________________________

3. Why are the peaks opposite in direction?

___________________________________________________________

___________________________________________________________

___________________________________________________________

4. Why is the second peak larger?

___________________________________________________________

___________________________________________________________

___________________________________________________________

5. Do your results support your predictions?

___________________________________________________________

______________________________________________________________________________________________________________________


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456 Student R esponse Sheet



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