Capacitor Energy (E) and RC Time Constant Calculator

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Capacitor is a passive component used to store and release electrical energy (Similar to a battery). It consists of two conductive plates separated by an insulating material called a dielectric. When a voltage is applied across the plates, an electric field forms in the dielectric, causing positive and negative charges to accumulate on the plates. This accumulation of charge creates an electric potential difference between the plates, resulting in the storage of electrical energy in the capacitor’s electric field.

The main characteristics of a capacitor are its capacitance (C) and voltage rating. Capacitance is a measure of the capacitor’s ability to store charge, and it is measured in farads (F). A one-farad capacitor can store one coulomb (1 C) of charge when a voltage of one volt (1 V) is applied across its plates. Capacitors come in various capacitance values, ranging from picofarads (pF) to farads (F), depending on the application.

Capacitors are utilized in a wide range of electronic and electrical applications due to their unique properties and functionality. Some common reasons why capacitors are used include:

  • Energy Storage
  • Filtering & Decoupling
  • Timing & Oscillation
  • Coupling & DC Blocking
  • Signal Coupling & AC Coupling
  • Start & Run Capacitors
  • Tuning & Filtering in Radios
  • Energy Conversion
  • Electronics Component Protection

Energy (E) & Time Constant (τ)

The energy stored in a capacitor is the amount of electrical energy that the capacitor can store when it is charged. When a capacitor is connected to a voltage source and charged, it accumulates electrical energy in its electric field. The energy stored in a capacitor is proportional to the capacitance of the capacitor and the square of the voltage across it.

An RC circuit is a combination of a resistor (R) and a capacitor (C) connected in series or parallel. When the capacitor is charging or discharging through the resistor, it takes a certain amount of time for the voltage across the capacitor to reach approximately 63.2% (1 – 1/e) of its final value. This time duration is called the time constant (τ) of the RC circuit.

Use this online calculator to find the energy stored in a capacitor (E) and the time constant (RC) based on the voltage across the capacitor. With the capacitor energy and time constant calculator, you can easily calculate two different values. Here, you can determine the time constant (T) by inputting the values for capacitance (C) and load resistance (R). Along with this, you can determine the energy stored in the capacitor (E) by entering the voltage (V), capacitance(C), and load resistance(R) values.

Voltage across capacitor
Load Resistance


\[E = \frac {V^2 * C}{2}\]
\[\tau = R * C\]

where :

  • E =Stored Energy (Joules)
  • τ = Time Constant (S)
  • V = Voltage (V)
  • C = Capacitance (uF)
  • R = Load Resistance (Ohms)

Any questions? Drop them here!