About this Calculator:

This calculator determines the energy stored in a capacitor and the time constant of an RC circuit.

Energy (E) is calculated using the formula: E = 0.5 × C × V², where C is the capacitance and V is the voltage.

Time Constant (T) is determined by T = R × C, where R is the series resistance and C is the capacitance.

These calculations help understand capacitor behavior in electrical circuits, especially for charging and discharging analysis.

Capacitor Charge and Time Constant Calculator: A Complete Guide

Introduction: The Water Tank Analogy

Imagine you have a water tank with a rubber membrane in the middle separating the top and bottom halves. If you pour water into the top half, pressure builds up against the membrane. The more water you add, the more tension is stored in the membrane. But if you release a valve, the water will rush down, returning the system to balance.

A capacitor works similarly—it stores electrical energy just like a tank stores water pressure. Instead of a rubber membrane, it uses an electric field between two conductive plates, and instead of water, it holds an electric charge. When needed, it can quickly release stored energy, making it a critical component in circuits.

What is a Capacitor?

A capacitor is a device that stores and releases electrical energy. It has two metal plates with an insulating material (called a dielectric) between them. The amount of charge it can store is called capacitance (C) and is measured in farads (F).

Types of Capacitors

• Ceramic Capacitors – Used in high-frequency applications.
• Electrolytic Capacitors – Store large amounts of charge, commonly found in power supply circuits.
• Film Capacitors – Used in high-voltage applications.
• Supercapacitors – Provide extremely high capacitance, used in energy storage systems.

How Does a Capacitor Work?

1. Charge Builds Up – One plate gains electrons and becomes negatively charged (-Q), while the other loses electrons and becomes positively charged (+Q).
2. Electric Field Forms – A voltage (V) develops across the plates, storing energy in an electric field.
3. Charging Stops at Max Voltage – When the voltage across the capacitor equals the supply voltage, no more current flows, and the capacitor is fully charged.
4. Energy Can Be Released – If a load is connected, the capacitor discharges, releasing stored energy into the circuit.

Capacitor Charge and Energy Calculations

1. How to Calculate Capacitor Charge (Q)

The charge stored in a capacitor depends on its capacitance (C) and the applied voltage (V):

Q = C × V

2. How to Calculate Energy Stored in a Capacitor (E)

E = (1/2) × C × V²

Capacitor Charge Calculation Examples

Example 1: Finding the Capacitor Charge

A 5 Farad capacitor is connected to a 50mV (0.05V) power source.

Q = 5 × 0.05 = 0.25C

Capacitor Time Constant (τ) and Charging Time

τ = R × C

Example: Charging Time Calculation

A 1000 µF (0.001F) capacitor is connected to a 3000Ω resistor.

τ = 3000 × 0.001 = 3s

Time to fully charge = 5 × τ = 15s

Capacitor Charge and Time Constant Calculator

How to Use the Calculator:

• Enter Capacitance (C) – Select the appropriate unit.
• Enter Voltage (V).
• Enter Resistance (R) (optional for time constant calculation).
• Get Instant Results.