1. What is the RC Charging Equation?

The RC charging equation describes how the voltage across a capacitor increases over time when connected to a voltage source through a resistor. It's fundamental in electronics for timing circuits, filters, and signal processing.

2. How Does the Calculator Work?

The calculator uses the RC charging equation:

Where:

• \( V_c \) — Voltage across capacitor (volts)
• \( V \) — Source voltage (volts)
• \( t \) — Time (seconds)
• \( R \) — Resistance (ohms)
• \( C \) — Capacitance (farads)
• \( e \) — Euler's number (~2.71828)

Explanation: The equation shows exponential approach to the source voltage, with time constant τ = RC (63.2% of final voltage at t = τ).

3. Importance of RC Time Constant

Details: The RC time constant (τ = R×C) determines how quickly the capacitor charges. After 5τ, the capacitor is considered fully charged (99.3% of source voltage).

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What happens when t = RC?
A: At t = RC (one time constant), the capacitor reaches about 63.2% of the source voltage.

Q2: How does the curve look?
A: The charging curve is exponential - steep at first, then gradually approaching the source voltage.

Q3: What if I want to calculate discharge instead?
A: For discharge, use Vc = V₀ × e^(-t/RC), where V₀ is initial voltage.

Q4: What are practical applications?
A: Used in timing circuits, power supply filters, audio crossovers, and many electronic timing applications.

Q5: How accurate is this model?
A: This assumes ideal components. Real capacitors have ESR (equivalent series resistance) that affects charging.