Capacitor Discharge Current Calculator

Capacitor Discharge Current Formula:

\[ I = \frac{V_0}{R} e^{-t / RC} \]

Initial Voltage (V₀):

Resistance (R):

Time (t):

Capacitance (C):

Discharge Current (I):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is the Capacitor Discharge Current Formula?

The capacitor discharge current formula calculates the instantaneous current flowing through a capacitor as it discharges through a resistor. This exponential decay model is fundamental to understanding RC circuits in electronics.

2. How Does the Calculator Work?

The calculator uses the capacitor discharge current formula:

\[ I = \frac{V_0}{R} e^{-t / RC} \]

Where:

\( I \) — Discharge current (A)
\( V_0 \) — Initial voltage across the capacitor (V)
\( R \) — Resistance (Ω)
\( t \) — Time since discharge began (s)
\( C \) — Capacitance (F)
\( e \) — Euler's number (approximately 2.71828)

Explanation: The formula describes how current decreases exponentially over time as the capacitor discharges through the resistor.

3. Importance of Discharge Current Calculation

Details: Calculating discharge current is essential for designing timing circuits, power supply systems, and understanding the behavior of capacitive elements in electronic systems.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What is the time constant (τ) in an RC circuit?
A: The time constant τ = R × C represents the time it takes for the current to decrease 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, but after 5 time constants (5RC), the current drops to less than 1% of its initial value.

Q3: Can this formula be used for charging capacitors?
A: No, this formula is specifically for discharge. Charging follows a different exponential growth pattern.

Q4: What happens if the resistance is zero?
A: The formula becomes undefined as resistance approaches zero. In practice, very low resistance causes extremely rapid discharge.

Q5: Does this formula account for capacitor ESR?
A: No, this ideal formula assumes a perfect capacitor with no equivalent series resistance (ESR).