Analog and electronic circuits

How does the magnitude of a capacitor's impedance (capacitive reactance) change as frequency increases?

  1. AIt increases
  2. BIt decreases
  3. CIt does not change
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Answer: B. It decreases

The impedance of a capacitor has magnitude 1/(2πfC), which decreases as the frequency f increases. A capacitor blocks DC (f = 0) and passes higher frequencies more easily. Filters and bypass capacitors make use of this property.

  • A. An inductor's impedance is the one that increases with frequency.
  • B. Correct. Since it is 1/(2πfC), it decreases at higher frequencies.
  • C. A capacitor's impedance depends strongly on frequency.
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