Capacitance Calculator
Calculate series/parallel capacitance, stored energy, reactance, and RC time constants
Enter values like: 100pF, 10nF, 1uF, 100μF
Quick Reference:
- Series: Total capacitance decreases (opposite of resistors)
- Parallel: Total capacitance increases (add all values)
- Units: 1F = 1000mF = 1,000,000μF = 10⁹nF = 10¹²pF
- 5τ rule: Capacitor is ~99.3% charged after 5 time constants
Understanding Capacitors
Capacitors store electrical energy in an electric field between two conducting plates. Their capacity to store charge is measured in farads (F), though practical capacitors are usually in microfarads (μF), nanofarads (nF), or picofarads (pF).
Series Capacitors
When capacitors are connected in series, the total capacitance decreases:1/Ctotal = 1/C1 + 1/C2 + 1/C3 + ...This is opposite to resistors! Series capacitors share the same charge but divide the voltage.
Parallel Capacitors
When capacitors are connected in parallel, their capacitances add up:Ctotal = C1 + C2 + C3 + ...This is also opposite to resistors. Parallel capacitors share voltage but can store more total charge.
Stored Energy
A charged capacitor stores energy in its electric field. The formulaE = ½CV² shows that energy increases with the square of voltage. This is why capacitors can deliver high currents quickly, making them useful for camera flashes and power supplies.
Capacitive Reactance
In AC circuits, capacitors oppose current flow with reactance:Xc = 1/(2πfC). Unlike resistance, reactance depends on frequency - capacitors pass high frequencies more easily than low frequencies, which is why they're used in filters.
RC Time Constant
When a capacitor charges through a resistor, the time constantτ = RC determines the charging rate. After one time constant, the capacitor reaches 63.2% of full charge. After 5τ, it's approximately 99.3% charged.
Common Capacitor Values
- Power supply filtering: 100μF - 10,000μF
- Decoupling: 0.1μF (100nF)
- Timing circuits: 1nF - 100μF
- RF circuits: 1pF - 100pF