Working Principle of Capacitor – How a Capacitor Works

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How a capacitor works? To demonstrate working principle of capacitor, let us consider a most basic structure of a capacitor. Because of it affects working principle of capacitor. So, read this article carefully.

It is made of two parallel conducting plates separated by a dielectric that is parallel plate capacitor. When we associate a battery (DC Voltage Source) over the capacitor, one (plate-I) gets appended to the positive end, and another (plate-II) to the negative end of the battery.

Working Principle of Capacitor – How a Capacitor Works

Now, the potential of that battery is applied across that capacitor. At that situation, plate-I is in positive potency with respect to the plate-II. At unfaltering state condition, the current from the battery attempts to move through this capacitor from its positive (plate-I) to negative (plate-II) however can’t flow because of the partition of these plates with a protecting material.

An electric field appears across the capacitor. As time goes on, positive plate (plate I) positive (plate I) will amass positive charge from the battery, and negative (plate II) will collect negative charge from the battery. After a certain time, the capacitor holds greatest measure of charge according to its capacitance regarding this voltage. This time length is called charging time of this capacitor.

After removing this battery from this capacitor, these two plates hold positive and negative charge for a specific time. Accordingly this capacitor goes about as a source electrical energy.


If two ends (plate I and plate II) are connected to a load, a current will flow through this load from plate-I to plate-II until all charges get vanished from both plates. This time span is known as discharging time of the capacitor.

discharging capacitor

With that’s working principle, a capacitor works better. Now, we will discuss work working principle of capacitor in a DC circuit and AC circuit. Let’s see below:

See Also: Capacitor or Capacitance: Definition and Formula

Working Principle of Capacitor in a DC Circuit

Suppose a capacitor is connected across a battery through a switch.

When the switch is ON, i.e., at t = +0, a current will begin flowing through this capacitor. After a specific time (i.e. charging time) never enable current to flow through it further.

It is because of the maximum charges is amassed on the two plates and capacitor goes about as a source which has a positive end associated with the positive end of the battery and has a negative end associated with the negative end of the battery with a similar power.

Due to zero potential difference among battery and capacitor, no current will flow through it. So, it can be said that initially a capacitor is short-circuited and finally open circuited when it gets connected across a battery or DC source.

See Also: Energy Stored in a Capacitor

Working Principle of Capacitor in an AC Circuit

Suppose a capacitor is connected across an AC source. Consider, at a certain moment of portion of this exchanging voltage, plate-I gets positive extremity and plate-II negative extremity. Just at that moment, plate-I accumulates positive charge and plate-II accumulates negative charge.

But at the negative half of this applied AC voltage, plate-I gets a negative charge and plate-II positive charge. There is no flow of electrons between these two plates because of dielectric put between the plates however they change their polarity with the difference in polarity. The capacitor plates get charged and released on the other hand by the AC.

See Also: Capacitor in Series and Parallel Voltage Explained

Working Principle of Capacitor Conclusion

After going through the above consider a most basic structure of a capacitor we can now establish working principle of capacitor. I hope you enjoy when reading this article, thank you.