# Understand How Capacitors Work With the Help of Proper Diagrams

A capacitor is one of the important and basic electronic devices that is used for various purposes. Here's some information that will help you in understanding how capacitors work.

ScienceStruck Staff

Last Updated: Oct 03, 2018

**C = ( ɛ**_{0}ɛ_{r}A )/dwhere,

- ɛ
_{0}is the permittivity in free space, which is approximately equal to 8.85 × 10^{-12}F/m, - ɛ
_{r}is the dielectric constant or relative permittivity, - A is the area of the plates and
- d is the distance between the plates

^{18}electrons)

**C = Q/V**

Breakdown Voltage

Breakdown voltage is the maximum voltage that can be applied across this device and if the voltage is increased beyond the breakdown voltage, the insulator (dielectric) between the plates of this electronic device will break and the device will begin to conduct.

Reactance

The reactance (X

X

where,

_{c)}offered by such a device is given by the formula below.X

_{c}= 1 / wC = 1 / 2 π f Cwhere,

- π is 22/7,
- w is the resonant frequency,
- f is the frequency and
- C is the capacitance

Why Do These Devices Block Direct Current?

We know that the frequency of direct current (DC) is zero. So, by substituting the value of zero frequency to the above equation, the value of reactance is infinite. This means that, the reactance offered by the device to a DC signal is infinite and so it does not allow DC to pass through it.

X

_{c}= 1 / wC

= 1 / 2 π f C

= 1 / 2 × π × 0 × C

= 1 / 0

= infinity

Capacitors in Series and Parallel Connection

✦ The mathematical equation of Ohm's law is I = V/R, where, I is the current flowing in the circuit, V is the voltage and R is the resistance offered by the element in the circuit. Replacing the resistance with capacitor, the formula is derived.

Capacitors in Series

The current passing through the circuit is denoted by i. In series connection, voltage changes but current remains the same.

By using Ohm's law,

i=C

i(1/C

i= (C

Thus, C

By using Ohm's law,

i=C

_{1}(dv_{1}/dt); i=C_{2}(dv_{2}/dt)i(1/C

_{1}+1/C_{2})=d(v_{1}+v_{2})/dti= (C

_{1}.C_{2}/ (C_{1}+C_{2})dv/dtThus, C

_{series}=(C_{1}.C_{2})/ C_{1}+C_{2}Capacitors in Parallel

The current passing through C

i

_{1}is i_{1}and the current passing through C_{2}is i_{2}. In this connection, the voltage remains the same, but the current varies. By Ohm's law,i

_{1}=C_{1}dv/dt, i_{2}=C_{2}dv/dt and the total current i= i_{1}+i_{2}=(C_{1}+C_{2})dv/dt Thus, C_{parallel}= C_{1}+C_{2}Functions

- As this device can block DC, it can be used as a filter in some electronic circuits.
- It can withstand any change in voltage applied, as it can charge and discharge at any time.

- They are used in a rectifier circuit (converts AC to DC) to remove the unwanted ripples in the output.
- It couples with the noise in the radio receiver circuit, thereby avoiding any disruption in the output.