A capacitor or electrical capacitor is a device that is used to store energy (electrical charge) in an internal electric field. It is a passive electronic component and its use is frequent in electronic circuits, as well as in analog and digital circuits.
Every capacitor has the same basic structure: two conductive plates separated by an insulating dielectric located between them. In them the energy charge is stored when an electric current flows and its dielectric must be made of a non-conductive material, such as plastic or ceramic.
When an electrical capacitor or condenser is placed in a circuit that has an active current, the electrons on the negative side accumulate on the plate that is closest to them. When the plate can no longer hold them, they pass to the dielectric and to the other plate, so the electrons are displaced back into the circuit, through a discharge.
The conductive plates of the capacitor are connected to the terminals of the passive element and the dielectric or insulating material is placed between the two plates, which store the electrical charge until a load is connected to the capacitor. The charge stored by a capacitor or capacitor is directly proportional to the voltage or tension applied. Also, its capacity is proportional to the area of the plate and inversely proportional to the distance between the two plates.
Another important factor of these devices is the capacitance, i.e., the ability of the component to store energy in the form of electrical charge. The capacitance value of an electrical capacitor is measured in farads and is the ratio of the stored electrical charge to the voltage (potential difference) between them.
The function of a capacitor is to store a charge of energy that can be released quickly. The charge and discharge of a capacitor is very useful for, for example, powering an electric motor and are very efficient in mechanisms that need a rapid increase in energy, such as the flash of a camera, starters for engines and car audio amplifiers.
In circuits where the voltage of the electric current fluctuates a lot, the function of the intermediate capacitor is to level it, since its charge stores the excess energy when the voltage increases. Subsequently, the energy stored in a capacitor is released as the voltage decreases.
Another function of a capacitor is to generate delays in electrical circuits in those activities that require it, by establishing delays in the flow of electric current. This is very useful when tasks are carried out at constant periods and at certain frequencies, or at certain time intervals.
In addition, a capacitor or capacitor can level the voltages of the electric current. If in a circuit with direct current voltage there are waves or ripples, the load of a large capacitor is able to absorb the peaks and fill the valleys. Thanks to this ability to regulate the frequency of electric current and create delays to give a certain rhythm to tasks, they have become a fundamental element in the development of electronic devices.
Due to their multiple uses and the variety of their electrical, physical and economic characteristics, there are currently a large number of types of capacitors. There are capacitors made with plates of various materials, with different shapes and a wide range of dielectrics. Among the most common are the electrolytic capacitor, the ceramic capacitor, series and parallel capacitors and the polyester capacitor, among others.
Electrolytic capacitor. This capacitor uses an electrolyte that acts as a first armature or cathode (negative electrode), which, upon receiving a suitable voltage, deposits an insulating layer on the anode (i.e. the tank or second armature). It is often used as an oscillator, as a frequency generator or to modulate the signal in power supplies.
Electrolytic capacitors release large amounts of energy in a short time, so it is used as a starting capacitor for electric motors that require high initial power. Although its capacity can be very high, an electrolytic capacitor does not work well with an alternating current, because the reverse polarization produces a short circuit between the electrolyte and the tank, so the temperature increases to such a degree that it can explode.
There are several types of electrolytic capacitors, according to their components (electrolytes and second armature), among them are aluminum and tantalum:
· Aluminum capacitor or capacitor: it is a polarized capacitor in which the electrolyte is a boric acid solution and its tank is made of aluminum. Its optimum performance is at low frequencies and is usually used in audio equipment and switching power supplies.
· Tantalum or tantalum capacitor or capacitor. It uses tantalum as an anode and has a better capacitance per volume than an aluminum electrolytic capacitor, since using this chemical element makes the dielectric layer very thin.
· Polyester capacitor: These capacitors have high power and are very fast responding. As a dielectric element they have thin polyester films and use aluminum to form their armatures. Their most common uses are in applications of connection and disconnection of direct current, to filter low tolerance signals and audio systems. They have advantages over paper capacitors because of their ability to reduce their size, in addition to having high efficiency and low power loss.
· Ceramic capacitor: They use different types of ceramics as dielectric element and can be formed by a single dielectric sheet or by stacked sheets. Depending on their characteristics, they can operate at different frequencies, including microwaves. Thanks to the specific properties of ceramics, they have very low losses.
· Series and parallel capacitors: Those referred to as "in series" are two or more capacitors connected in a line. The positive of each capacitor is connected to the negative plate of the next capacitor and they have the same charge and equal charging current. For their part, parallel capacitors are also two or more capacitors, but connected in parallel, since their terminals are connected to the terminal of another capacitor or capacitors. They have the same voltage, as well as a common voltage supply.
Imagen: Eric Schrader from San Francisco, CA, United States, CC BY-SA 2.0 <https://creativecommons.org/licenses/by-sa/2.0>, via Wikimedia Commons
