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Capacitive reactance

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College Physics I – Introduction

Definition

Capacitive reactance is the opposition that a capacitor presents to alternating current. It is inversely proportional to both the frequency of the AC signal and the capacitance.

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5 Must Know Facts For Your Next Test

  1. Capacitive reactance ($X_C$) is given by the formula $X_C = \frac{1}{2\pi f C}$, where $f$ is the frequency in hertz and $C$ is the capacitance in farads.
  2. The unit of capacitive reactance is ohms (Ω).
  3. As frequency increases, capacitive reactance decreases.
  4. Capacitive reactance causes a phase shift where the current leads the voltage by 90 degrees in an ideal capacitor.
  5. In AC circuits, capacitive reactance impacts the total impedance.

Review Questions

  • What happens to capacitive reactance when the frequency of an AC signal increases?
  • How do you calculate capacitive reactance for a given frequency and capacitance?
  • What phase relationship does capacitive reactance create between current and voltage?
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