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Physics

Capacitor Energy

E = ½CV². Free online Capacitor Energy. Calculate capacitor energy online — fast, accurate, mobile-friendly, no signup needed.

E = ½·C·V².
Energy (J)
0.072

Derivation

  1. ├── 01GivenC = 0.001, V = 12
  2. ├── 02Formula{let t=e.C,a=e.V;return.5 × t × a²}
  3. ├── 03Substitute{let t=e.0.001,a=e.12;return.5 × t × a²}
  4. └── 04Compute Energy (J)0.072
Did you know?

The phrase "kinetic energy" was coined by William Thomson (Lord Kelvin) and Peter Guthrie Tait in 1867 — before that physicists called it vis viva, "living force".

§01What is

Understanding the Capacitor Energy

The Capacitor Energy computes Energy (J) from 2 inputs: capacitance (f), voltage. E = ½CV².

Physics is the toolkit for turning a real-world observation into a prediction. Whether it’s a falling object, a moving car, or a stressed beam, the equations here are the same ones every engineer relies on. The Capacitor Energy sits in that toolkit — it E = ½CV². Enter your numbers above and the result updates instantly; every step of the math is shown in the Derivation panel so you can see exactly how the answer was reached.

§02The Formula

How it’s calculated

{let t=e.C,a=e.V;return.5 × t × a²}

Where

C
Capacitance (F)
V
Voltage
§03Practical Example

Step-by-step walkthrough

Scenario

Apply the formula to a realistic set of inputs: Capacitance (F) = 0.001, Voltage = 12.

  1. 01Start by noting the input — Capacitance (F): 0.001.
  2. 02Start by noting the input — Voltage: 12.
  3. 03Substitute these values into the formula: {let t=e.C,a=e.V;return.5 × t × a²}
  4. 04Compute Energy (J): the calculator returns 0.072.
  5. 05Cross-check the answer by opening the Derivation panel above — every line of math is shown so you can follow the computation end-to-end.
§04Variants

Common Capacitor Energy Problems

The formula gets rearranged depending on which variable you need. Here are the patterns you’ll run into in the real world — find the one that matches your problem and follow the worked steps.

01 · PATTERN

Capacitance (F) halved

C = 0.0005 (from 0.001)

Keep every other input at its default and halve the capacitance (f). See how energy (j) responds.

  1. 01New Capacitance (F): 0.0005
  2. 02Baseline Energy (J): 0.072
  3. 03New Energy (J): 0.036
  4. 04Energy (J) decreases by 50% → use this sensitivity to plan for real-world variation.
02 · PATTERN

Capacitance (F) doubled

C = 0.002 (from 0.001)

Keep every other input at its default and double the capacitance (f). See how energy (j) responds.

  1. 01New Capacitance (F): 0.002
  2. 02Baseline Energy (J): 0.072
  3. 03New Energy (J): 0.144
  4. 04Energy (J) increases by 100% → use this sensitivity to plan for real-world variation.
03 · PATTERN

Voltage halved

V = 6 (from 12)

Keep every other input at its default and halve the voltage. See how energy (j) responds.

  1. 01New Voltage: 6
  2. 02Baseline Energy (J): 0.072
  3. 03New Energy (J): 0.018
  4. 04Energy (J) decreases by 75% → use this sensitivity to plan for real-world variation.
04 · PATTERN

Voltage doubled

V = 24 (from 12)

Keep every other input at its default and double the voltage. See how energy (j) responds.

  1. 01New Voltage: 24
  2. 02Baseline Energy (J): 0.072
  3. 03New Energy (J): 0.288
  4. 04Energy (J) increases by 300% → use this sensitivity to plan for real-world variation.
§05FAQ

Frequently asked questions

Yes. The calculator implements the standard formula as documented and returns exact floating-point results. No approximations are used unless noted in the formula.
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