In the previous post, we discussed about the basic theory behind the capacitor. In this post, we will understand “ How capacitor works ”.

As we have discussed earlier, when an electric power is provided to the capacitor, the capacitor starts accumulating the electrical charge.

As soon as the power goes off, it slowly discharges the accumulated charge.

I hope now you are getting a rough idea about “how capacitor works”. Lets take an example. In the below mentioned animation, We have an LED which is connected in a bread board along with a capacitor, a resistor and a switch.

When the switch is placed in ON condition, the LED gets the supply and glows brightly. However, when the supply is cut off by placing the switch in OFF condition, the LED does not turn off as it would be in case the capacitor was not in the circuit. Instead, the LED still glows and fades slowly. At this point of time, the capacitor is providing power to the LED. As the capacitor discharges gradually, the brightness of LED also fades. As soon as the capacitor is completely discharged, the LED turns OFF.

Now, a question may arise in your mind. Why we use resistors with capacitors? The answer is very simple. When we use a resistor in capacitor circuit, the charging of capacitor takes place more slowly. But the biggest advantage is this that post charging, the capacitor discharges also very slowly. This is due to the fact that the greater the value of resistance will be, the less quantity of charge will pass through it; and hence the more time will be consumed in the charging and discharging of the capacitor. In this way we can use a capacitor with a resistor as a timer. This method of providing time delay is cheap and simple also.

A capacitor can be used for many purposes. Few of them are :

  • Can be used with a resistor as a timer. One of the most popular examples for this is Russians. Russians have used capacitors for inducing a time delay in weapon control circuits for many years.
  • To quench unwanted current spikes in electronic circuits. For example – capacitors are still used in music players for filtering the unwanted noise due to current spikes.
  • Can be used to avoid unwanted triggering of an electronic circuit due to the current spikes.
  • Capacitor is used to create a phase difference in the power source. For example – Single phase motors using capacitors to get a phase difference.