Calculate capacitance, charge, energy, reactance, and RC time constant. Interactive charge/discharge curve with series and parallel combinations and unit conversions.
Capacitors are one of the three fundamental passive electronic components (along with resistors and inductors). They store energy in an electric field between two conductive plates separated by a dielectric material. From tiny 1pF ceramic capacitors in RF circuits to massive 10,000µF electrolytic capacitors in power supplies, understanding capacitor calculations is essential for any electronics work.
| Type | Range | Polarized | Best For |
|---|---|---|---|
| Electrolytic (Al) | 0.1–10,000 µF | Yes | Power supply filtering |
| Ceramic (MLCC) | 1 pF – 100 µF | No | Bypass, decoupling, RF |
| Film | 1 nF – 100 µF | No | Audio, timing, precision |
| Tantalum | 0.1–1,000 µF | Yes | Compact SMD, stable |
| Supercapacitor | 0.1–3,000 F | Yes | Energy storage, backup |
| Mica | 1 pF – 10 nF | No | High-frequency, precision |
When a capacitor charges through a resistor, it follows an exponential curve. The time constant τ = R × C is the time to reach 63.2% of supply voltage. Key milestones: at 1τ = 63.2%, 2τ = 86.5%, 3τ = 95.0%, 4τ = 98.2%, 5τ = 99.3% (considered "fully charged"). The discharge curve is the mirror image — at 1τ, voltage drops to 36.8% of initial value.
Capacitance spans an enormous range — from picofarads (10⁻¹² F) in radio circuits to thousands of farads in supercapacitors. The conversion chain: 1 F = 1,000 mF = 1,000,000 µF = 10⁹ nF = 10¹² pF. Most common values: electrolytic capacitors in µF (10–10,000), ceramic capacitors in nF or pF (10pF–100nF), and film capacitors in nF to µF range.