How To Calculate Capacitor Discharge

Capacitor Discharge Formula:

\[ V = V_0 \times e^{-t / (R \times C)} \]

Initial Voltage (V0):

Time (t):

Resistance (R):

Capacitance (C):

Discharge Voltage (V):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What Is Capacitor Discharge?

Capacitor discharge refers to the process where a capacitor releases its stored electrical energy through a circuit. The voltage across the capacitor decreases exponentially over time as it discharges through a resistor.

2. How Does The Calculator Work?

The calculator uses the capacitor discharge formula:

\[ V = V_0 \times e^{-t / (R \times C)} \]

Where:

\( V \) — Voltage at time t (V)
\( V_0 \) — Initial voltage (V)
\( t \) — Time since discharge began (s)
\( R \) — Resistance (Ω)
\( C \) — Capacitance (F)
\( e \) — Euler's number (~2.71828)

Explanation: The formula describes the exponential decay of voltage across a capacitor as it discharges through a resistor. The product R×C is known as the time constant (τ) of the circuit.

3. Importance Of Capacitor Discharge Calculation

Details: Understanding capacitor discharge is crucial for designing timing circuits, power supply systems, and electronic filters. It's also essential for safety considerations in high-voltage systems.

4. Using The Calculator

Tips: Enter initial voltage in volts, time in seconds, resistance in ohms, and capacitance in farads. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the time constant in RC circuits?
A: The time constant (τ = R×C) represents the time it takes for the voltage to drop to approximately 36.8% of its initial value.

Q2: How long does it take for a capacitor to fully discharge?
A: Technically, a capacitor never fully discharges in finite time, but after 5 time constants (5RC), the voltage drops to less than 1% of its initial value.

Q3: Can this formula be used for charging capacitors?
A: No, the charging formula is different: V = V₀(1 - e^(-t/RC)) for charging through a resistor.

Q4: What happens if the resistance is very small?
A: With very small resistance, the discharge occurs very quickly, which can create large current spikes that may damage components.

Q5: Are there practical applications of capacitor discharge?
A: Yes, capacitor discharge is used in camera flashes, defibrillators, pulse generators, and many timing circuits in electronics.