Energy Stored by Capacitor: How to Calculate the Energy Stored in Capacitor? (For CBSE, ICSE, IAS, NET, NRA 2022)

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Title: Energy Stored by Capacitor

  • Dramatization that is usually seen in movies where medical personnel use a defibrillator to pass an electric current through a patient՚s heart to get it to beat normally uses the energy stored in a capacitor.
  • Less dramatic application of the energy stored in the capacitor lies in the use of capacitors in microelectronics, such as handheld calculators.

How to Calculate the Energy Stored in Capacitor?

How to Calculate the Energy Stored in Capacitor?
  • Work must be done to transfer charges onto a conductor, against the force of repulsion from the already existing charges on it.
  • The energy stored in a capacitor is nothing but the electric potential energy and is related to the voltage and charge on the capacitor.
  • If the capacitance of a conductor is C, then it is initially uncharged and it acquires a potential difference V when connected to a battery.
  • If q is the charge on the plate at that time, then

  • The work done is equal to the product of the potential and charge.
  • This work done to charges from one plate to the other is stored as potential energy of the electric field of the conductor.


If the battery delivers a small amount of charge dQ at a constant potential V, then the work done is

Work done

Now the total work done in delivering a charge of an amount q to the capacitor is given by,

Therefore, the energy stored in capacitor is given by,

Substituting ,

Applications of Capacitor Energy

  • The audio equipment, uninterruptible power supplies, camera flashes, pulsed loads such as magnetic coils and lasers use the energy stored in the capacitors.
  • Super capacitors can store a large amount of energy and can offer new technological possibilities.
  • A defibrillator that is used to correct abnormal heart rhythm delivers a large charge in a short burst to a person՚s heart.
  • Applying large shocks of electric current can stop the arrhythmia and allow the body՚s natural pacemaker to resume its normal rhythm.
  • A defibrillator uses the energy stored in the capacitor
  • Energy storage
  • Pulsed power and weapons
  • Power conditioning
  • Power factor correction
  • Suppression and coupling
  • Motor starters
  • Sensing
  • Oscillators