Electricity & Magnetism
Capacitive Reactance
Opposition to AC current flow by a capacitor.
Variables
XCΩ
Capacitive reactance
Opposition to AC by capacitor
In SI units: kg·m²/(A²·s³)
Allowed values: greater than 0
ωrad/s
Angular frequency
ω = 2πf
In SI units: s⁻¹
Allowed values: greater than 0
CF
Capacitance
Capacitance
In SI units: A²·s⁴/(kg·m²)
Allowed values: greater than 0
Derivation
From I = C(dV/dt) for V = V₀sin(ωt), X_C = V₀/I₀ = 1/(ωC).
Your notes
0/5000
Check value
Round inputs run through this page's calculator. Use it to test your own working or a rearranged form. It is a test case, not a real-world example.
- ω = 2 rad/s (Angular frequency)
- C = 3 F (Capacitance)
Result: XC = 0.16666667 Ω
Other electricity & magnetism formulas with the same quantities
- Resonant Frequency (LC) (AC Circuits) shares Capacitance
- Capacitance (Capacitance) shares Capacitance
- Parallel Plate Capacitor (Capacitance) shares Capacitance
- Capacitor Energy (Capacitance) shares Capacitance
- RC Time Constant (Capacitance) shares Capacitance
- Capacitor with Dielectric (Capacitance) shares Capacitance
Where this formula is listed
- Electricity & Magnetism formulas, under AC Circuits, alongside RMS Voltage/Current.
- In the electricity & magnetism list it comes after RMS Voltage/Current and before Inductive Reactance.
- Electricity & Magnetism formula sheet, one of 48 formulas printed with symbol keys and SI units.
- The full formula index, grouped by category and topic.
Common questions
What is the Capacitive Reactance formula?
Capacitive Reactance is written X_C = 1/(ωC). Opposition to AC current flow by a capacitor. It belongs to Electricity & Magnetism, under AC Circuits.
What are the units in X_C = 1/(ωC)?
In SI units, X_C is capacitive reactance, measured in kg·m²/(A²·s³); ω is angular frequency, measured in s⁻¹; C is capacitance, measured in A²·s⁴/(kg·m²).
How is the Capacitive Reactance formula derived?
From I = C(dV/dt) for V = V₀sin(ωt), X_C = V₀/I₀ = 1/(ωC). The result is X_C = 1/(ωC).