MCAT Physics Question 90: Answer and Explanation

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Question: 90

15. Which of the following best characterizes ideal voltmeters and ammeters?

  • A. Ideal voltmeters and ammeters have infinite resistance.
  • B. Ideal voltmeters and ammeters have no resistance.
  • C. Ideal voltmeters have infinite resistance, and ideal ammeters have no resistance.
  • D. Ideal voltmeters have no resistance, and ideal ammeters have infinite resistance.

Correct Answer: C

Explanation:

While this is primarily a recall question, it should also be intuitive. Voltmeters are attempting to determine a change in potential from one point to another. To do this, they should not provide an alternate route for charge flow and should therefore have infinite resistance. Ammeters attempt to determine the flow of charge at a single point and should not contribute to the resistance of a series circuit; therefore, they should have no resistance.

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