Capacitor Calculator

Q=CV is the fundamental capacitor equation where Q is charge (in coulombs), C is capacitance (in farads), and V is voltage (in volts). A capacitor stores electrical energy by accumulating opposite charges on two conductive plates separated by an insulator (dielectric). When voltage is applied, electrons flow onto one plate and away from the other, creating an electric field. A 100μF capacitor at 12V stores: Q = 100×10⁻⁶ × 12 = 1.2 millicoulombs of charge.

In parallel, capacitances add directly: C_total = C₁ + C₂ + C₃. This increases total capacitance because the plates effectively get larger. In series, reciprocals add: 1/C_total = 1/C₁ + 1/C₂ + 1/C₃. This decreases total capacitance but increases voltage rating. Example: Three 100μF capacitors in parallel = 300μF. The same in series = 33.3μF. Use parallel for more capacitance, series for higher voltage handling.

Capacitive reactance (Xc) is a capacitor's opposition to AC current, measured in ohms. Formula: Xc = 1/(2πfC), where f is frequency and C is capacitance. As frequency increases, reactance decreases—capacitors pass high frequencies more easily. At 60Hz, a 10μF capacitor has Xc = 265Ω. At 1kHz, the same capacitor has Xc = 16Ω. This property makes capacitors useful as high-pass filters in audio circuits and for blocking DC while passing AC.

Energy stored in a capacitor is E = ½CV², where C is capacitance and V is voltage. Energy increases with the square of voltage, so doubling voltage quadruples energy. A 1000μF capacitor at 50V stores: E = 0.5 × 0.001 × 50² = 1.25 joules. For comparison, a AA battery holds about 10,000 joules. Capacitors discharge energy very quickly (milliseconds), making them useful for camera flashes, defibrillators, and power supply smoothing.

Ceramic capacitors (1pF-1μF): Small, stable, used in high-frequency circuits and decoupling. Electrolytic capacitors (1μF-10,000μF): High capacitance, polarized, used in power supplies for smoothing. Film capacitors (1nF-10μF): Precise, stable, used in audio and timing circuits. Tantalum capacitors (0.1μF-1000μF): Compact, stable, used in portable electronics. Supercapacitors (1-3000F): Massive capacitance, used for energy storage and backup power. Choose based on required capacitance, voltage rating, and operating frequency.