# 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?

• 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.

Hence,

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

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