Conceptual Question 2
(Southwest Texas Junior College)

Background: This question is designed to come at the end of the unit on "bulbs and batteries" and is specifically targeting the pre-service and in-service teachers in class. The hands-on activities necessitate that instructors verify that "identical bulbs" are indeed identical when using the brightness of the bulbs as an indicator of the size of the current flowing through the circuit. Many bulbs in a batch are not the same resistance. Therefore this question was designed to help these teachers (and other students as well) understand that the exploratory observations will be significantly different if bulbs of different resistance are used in the circuit...the bulb brightness cannot be used as an indicator of current size.

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Which of the bulbs in the circuit drawn below shines the brightest? Explain your reasoning.

  1. bulb A
  2. bulb B
  3. bulb C
  4. they shine equally bright

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Contributors: Mary Beth Monroe, Margaret Messinger
Institution: SouthWest Texas Junior College
Target Audience: Physics students
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