Capacitor Guide

Basics of Capacitors [Lesson 1] How do capacitors work?

This is a technical article that aims to explain the basics of capacitors. 

The first lesson will give an overview of capacitors.

[Lesson 1: Overview of capacitors]

Talking about electrical circuits

Let's begin by talking about electrical circuits and about capacitors.

<A circuit is like a road; a charge is like a car.>

If we think of a circuit as a road, then the movement of the charge is like the movement of the cars along the road.


<A resistor is like a bumpy road.>

In the case of a road which is bumpy, the speed of the cars is reduced, but the cars continue to travel toward their intended destination. In the case of an electrical circuit, heat is generated by a resistor, resulting in an energy loss. since this is basic level information, I would delete this reference to Joule heat, as it is too technical.


<Power supplies (batteries) are devices that provide a potential difference.>

A power supply is a device that provides a potential difference of voltage E[V] at the two ends where it is connected. It is the same as a car which is automatically carried up by an elevator to the position of height t[m] without using its own power.(what is the basic meaning of t(m)


So what are capacitors?
Let's now talk about cases where capacitors have been connected to the power supplies.

<A capacitor is like a parking lot.>

The capacitor stores a charge. If we use the same analogy of the circuit and road, a capacitor will be a parking lot. The same number of charges are always stored at the plus and minus sides in an electronic circuit.


<What is a capacitor's capacity to store charges, i.e., electrostatic capacitance?>

The indicator used to express the extent to which a capacitor can store a charge is known as the electrostatic capacitance, and this can be calculated using equation (1).
As is clear from equation (1), the electrostatic capacitance can be increased by <1> increasing the electrode surface area S, <2> shorting the distance between the electrodes, and <3> using materials that have a high dielectric constant.

According to the International System of Units (SI), F (farad) is used as the unit of electrostatic capacitance. The capacitance produced if a charge of 1C (coulomb) is stored when a 1V voltage (potential difference) is applied to a conductor is defined as 1F.

<How a capacitor works>

What happens to the charge stored in a capacitor is that when switch S1 is set to OFF and switch S2 is set to ON, a current will flow to the load.


Thanks to the presence of a capacitor, a bulb will light stably even if the supply voltage is unstable. 


<Capacitors block the flow of direct current and permit the flow of alternating current.>

A capacitor does not allow direct current to pass through it, but when the charging and discharging are repeated, a charging current and discharging current repeatedly flow to the capacitor. When this phenomenon is observed from outside the capacitor, it appears as if the current is flowing through the capacitor.


By utilizing these characteristics, large numbers of capacitors are used in circuits. It is necessary to select the items that are optimally suited to the intended applications.

person in charge: Murata Manufacturing Co., Ltd.      Y.I & K.M

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