Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

This is an AMP page - Open full page! for all features.

Capacitors - Stored Energy

Sponsored Links

Capacitor - Energy Stored

The work done in establishing an electric field in a capacitor, and hence the amount of energy stored - can be expressed as

W = 1/2 C U2(1)


W = energy stored - or work done in establishing the electric field (joules, J)

C = capacitance (farad, F, µF )

U = potential difference (voltage, V)

Capacitor - Power Generated

Since power is energy dissipated in time - the potential power generated by a capacitor can be expressed as

P = dW / dt                    (2)


P = potential power (watts, W)

dt = dissipation time (s)

Example - Capacitor, energy stored and power generated

The energy stored in a 10 μF capacitor charged to 230 V can be calculated as

W = 1/2 (10 10-6 F) (230 V)2

= 0.26 J

in theory - if this energy is dissipated within 5 μs the potential power generated can be calculated as

P = (0.26 Joules) / (5 10-6 s)

= 52000 W

= 52 kW

Be aware that in any real circuit, discharge starts at a peak value and declines. The energy dissipated is a very rough average power over the discharge pulse.

Capacitor - Time to Discharge at Constant Power Load

The time to discharge a capacitor at constant power load can be expressed as

dt = 1/2 C (U s 2- Uf2) / P               (3)


dt = discharge time (s)

U s = start voltage (V)

Uf = final voltage (V)

Breakdown (puncture) Voltage

Puncture voltage at 1 MHz (V/mil, V/0.001 inch):

  • Air: 240
  • Alsimag: 240
  • Bakelite: 300
  • Bakelite, mica-filled: 325 - 375
  • Cellulose acetate: 250 - 600
  • Formica: 450
  • Glass, window: 200 - 250
  • Glass, Pyrex: 335
  • Mica, ruby: 3800 - 5600
  • Mycalex: 250
  • Plexiglas: 990
  • Polyethylene: 1200
  • Polystyrene: 500 - 700
  • Porcelain: 40 -100
  • Quartz, fused: 1000
  • Steatite, low-loss: 150 - 315
  • Teflon: 1000 - 2000
Sponsored Links

Related Topics


Electrical engineering with units, amps and electrical wiring. Wire gauges, electrical formulas, motors and more.


Climate, meteorology, solar, wind, emissions and environmental related engineering resources.

Related Documents


Capacitors and capacitance - charge and unit of charge.

Capacitors - Parallel and Serial Circuits

Parallel and serial connected capacitor circuits.

Energy Storage Density

Energy density - by weight and volume - for some ways to store energy

Relative Permittivity - the Dielectric Constant

Common materials and their relative permittivity.

Sponsored Links

Search Engineering ToolBox

  • the most efficient way to navigate the Engineering ToolBox!

SketchUp Extension - Online 3D modeling!

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp from the Sketchup Extension Warehouse!


We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.

Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.

Google use cookies for serving our ads and handling visitor statistics. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.

AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.