MCAT Physics Question 85: Answer and Explanation

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Question: 85

10. The energy stored in a fully charged capacitor is given by . In a typical cardiac defibrillator, a capacitor charged to 7500 V has a stored energy of 400 J. Based on this information, what is the charge on the capacitor in the cardiac defibrillator?

  • A. 1.1 × 10-5 C
  • B. 5 × 10-2 C
  • C. 1.1 × 10-1 C?
  • D. 3.1 × 106 C

Correct Answer: C

Explanation:

Because the question is asking us to calculate the charge on the capacitor, use the formula Q = CV. We are given V = 7500 V and can calculate C from the formula for energy,

:

Thus, the charge is close to 0.1 C, which is closest to choice (C).

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