Interactive Lecture Demonstrations
Prediction Sheet—Magnetic Forces
Directions:
Click here to download the
Prediction Sheet on which you will record your predictions. Write your name
at the top to record your presence and participation in these demonstrations.
For each demonstration, write your predictions on this sheet before making any
observations. You may be asked to send this sheet to your instructor.
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Demonstration
1:
A Van de Graaff generator is turned on, and it becomes positively
charged. A magnet is brought near the
generator as shown. Predict the
direction of the force exerted by the magnet on the charges on the Van de
Graaff. Only
after you have made your prediction, click here to
see the magnetic force. Compare the result to your prediction and explain any
differences. |
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Demonstration
2:
An insulated wire is in a magnetic field pointed into the screen. There is no electric current flowing
through the wire. Predict the direction of the force exerted by the magnetic
field on the electrons in the wire. Only after you have made your
prediction, click here to see the magnetic force.
Compare the result to your prediction and explain any differences. |
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Demonstration 3: Now the switch
is closed so that the current flows through the wire in the direction shown.
Predict the direction of the force exerted by the magnetic field on the electrons
in the wire. (Recall that the electrons move in the opposite direction to the
conventional current.) Only
after you have made your prediction, open the simulation: https://www.compadre.org/Physlets/electromagnetism/illustration27_4.cfm Click on the start button |
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Demonstration 4: Suppose that
the magnetic field is out of the screen. Now the switch is closed so that the
current flows through the wire in the direction shown. Predict the direction
of the force exerted by the magnetic field on the electrons in the wire. Only
after you have made your prediction, open the same simulation as in
Demonstration 3. Click on the start button |
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Demonstration 5: The magnetic
field is again into the screen as in Demonstration 3. Now the battery is
reversed so that the current flows through the wire in the opposite direction
(as shown). Predict the direction of the force exerted by the magnetic field
on the electrons in the wire. Only
after you have made your prediction, open the same simulation as in
Demonstration 3. Click
on Restart and then on the start button |
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Demonstration 6: In each of the situations shown, a positive charge is moving in a
magnetic field. Use the right-hand
rule to predict the direction of the force or magnetic field (whichever is
missing). |
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Only after making your prediction, click here to see the correct direction of the force. Compare
to your prediction, and explain any differences. |
Only after making your prediction, click here to see the correct direction of the force. Compare
to your prediction, and explain any differences. |
Only after making your prediction, click here to see the correct direction of the force. Compare
to your prediction, and explain any differences. |
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Demonstration 7: In Dewmonstration 6, suppose that the chrge were negative.
Again use the right-hand rule to predict the direction of
the force or magnetic field (whichever is missing). |
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Only after making your prediction, click here to see the correct direction of the force. Compare
to your prediction, and explain any differences. |
Only after making your prediction, click here to see the correct direction of the force. Compare
to your prediction, and explain any differences. |
Only after making your prediction, click here to see the correct direction of the force. Compare
to your prediction, and explain any differences. |
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