Calculate capacitive reactance (Xc) and impedance at any frequency. Visualize phase relationships and understand how capacitors behave in AC circuits.
Select capacitor value
Operating frequency
Xc = 1 / (2πfC)
φ = -90°
Current leads voltage by 90°
Capacitive Reactance
1.59 kΩ
Xc = 1 / (2πfC)
Phase Angle
-90°
Impedance
-j1.59 kΩ
Capacitive reactance (Xc) is the opposition that a capacitor presents to alternating current (AC). Unlike resistance, which dissipates energy as heat, reactance stores energy temporarily in an electric field and returns it to the circuit.
Xc = 1 / (2πfC)
In a pure capacitor circuit, the current leads the voltage by 90 degrees. This means current reaches its maximum value a quarter cycle before voltage does. This is expressed in complex notation as Z = -jXc.
Xc = ∞, capacitor blocks all DC current (open circuit)
High Xc, capacitor impedes current flow significantly
Low Xc, capacitor allows current to pass easily
Range: 1pF - 100µF
Frequency: DC to GHz
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Limitations:
Range: 1µF - 10,000µF
Frequency: DC to 100kHz
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Limitations:
Range: 100pF - 100µF
Frequency: DC to MHz
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Limitations:
Range: 100nF - 1000µF
Frequency: DC to 100kHz
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Capacitive reactance (Xc) is the opposition a capacitor presents to alternating current. It is measured in ohms and calculated using the formula Xc = 1/(2πfC), where f is frequency and C is capacitance. Unlike resistance, reactance depends on frequency.
As frequency increases, the capacitor charges and discharges more rapidly, allowing more current to flow. This is why Xc = 1/(2πfC) shows an inverse relationship with frequency. At DC (f=0), reactance is infinite, blocking all current.
In a pure capacitor, current leads voltage by 90 degrees. This is because current must flow to charge the capacitor before voltage can build up across it. This phase lead is represented by the -j in complex impedance notation.
Consider the operating frequency, required capacitance value, voltage rating, temperature coefficient, and ESR (Equivalent Series Resistance). For high-frequency applications, use ceramic or film capacitors. For power filtering, electrolytics are common.
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