Teaching Physics with the Physics Suite

Edward F. Redish

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What happens to the bulbs?

In the figure at the right is shown an electrical network containing a battery with EMF = E, and three resistors with resistances R1, R2, and R3. All three resistances are identical and have a resistance R. In the circuit is a switch, which is open when we start. In addition, two points in the network are marked with dots and the numbers "1" and "2".

  1. If the switch is open, rank the brightness of the bulbs.
  2. If the switch is open, calculate the current through the battery. (Express your answer in terms of the symbols given.)
  3. If the switch is closed, what happens to the brightness of each bulb? (Increase, Decrease, Same) Now rank the brightness of the three bulbs. Briefly explain your reasoning.
  4. If the switch is open and we connect the two terminals of an ammeter to the points 1 and 2, what would happen to the brightness of each of the bulbs? (Increase, Decrease, Same) Briefly explain your reasoning.

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Page last modified October 19, 2002: E17