PURPOSE: Simple paradoxical circuits to encourage thought and discussion about DC circuits.
DESCRIPTION: The circuits shown above are connected as shown with the switch for each open. What will happen when the switch is closed? Let students discuss each case before actually doing the experiment.
(Left) With the switch open the two lights on the right are equally bright and the light in the middle is off. Q: What happens to the three lights when the switch is flipped? A: Nothing. The potential is the same at the two points connected by the s witch.
(Right) A third battery is connected into the circuit when the switch is closed. Before the switch is closed both lights are equal in intensity. Q: What happens to the intensity of the lights when the switch is closed? A: Nothing. The point between the two bulbs remains at the same potential.
SUGGESTIONS:
EQUIPMENT: Two battery-operated circuit paradox demonstrations.
SETUP TIME: None.
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