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Difference between Capacitor and Battery

What is Capacitor?

A capacitor is a passive two-terminal device used to store electric charge in an electric field. The capacitor has two metallic plates separated by a dielectric medium. The dielectric medium may be paper,electrolytes,mica,tantalum etc.
When voltage is applied across the capacitor, the capacitor gets charged up to the voltage applied. The charge remains stored in the electric field and when the electric field is removed the stored charge vanishes after short period of time. The capacitor is a passive component.

What is Battery?

The battery is active component which supplies energy to the circuit. The battery can be charged by applying the voltage across the battery, and the stored energy can be used later on.
The battery consist of mainly three parts- Anode, Cathode and Electrolyte. The charging and discharging of the battery takes place by chemical reaction. The key difference between capacitor and battery is as given below.

Key Differences between battery and capacitor 

  • When voltage is applied electric field F=qE is generated between the plates of the capacitor. The potential energy is stored in the capacitor. Whereas, the energy is stored in the form of chemical energy in the battery.
  • Capacitor draws energy from the source, stores it till voltage is applied across it and on switching off the supply capacitor release the energy. In the case of battery, it draws energy from the source and after getting fully charged if the incoming supply gets tripped it delivers energy to the load.
  • The capacitor is a passive component. It can not be used  as a voltage source. The battery delivers current to the load circuit for a longer time period. That is why battery is a active component.
  • Capacitor is generally used for AC circuit.It blocks the DC components of the circuit. The battery can be charged with DC supply because chemical reaction between electrolyte and the plates takes place in the form of the chemical reactions when DC is applied. The battery can not be charged with AC supply.
  • The capacitor discharge quickly because of lesser time constant. The resistance is approximate zero. In the case of battery discharges exponentially and it discharges slowly.
  • Charging and discharging of the capacitor is very fast, and it takes about 1-10 seconds. It takes large current to charge. The battery charging and discharging time is slow and it takes about 1-2 hrs for charging and discharging of battery. When battery is fully discharged it is charged on boost mode of the battery charger, and after attaining certain voltage the battery is charged in trickle/float mode of the battery charger.
  • Life cycle of the capacitor is more than battery. The life cycle of capacitor and battery is 30000 hours and 500 hours respectively. Also, the cost of the capacitor is more than the battery.
  • The specific power of capacitor is about 10000(w/Kg) and specific power of the battery is 1000 to 3000(w/Kg).
  • The capacitor can function in the temperature range of -10 to 65 degree centigrade, whereas in the case of battery it is 0 to 45 degree centigrade.
  • Capacitor is larger in size as compared to battery.