What is Capacitor? Capacitor in parallel, Capacitor in Series, Working principle of capacitor, Ceramic capacitor applications, polarized capacitors, film capacitors, unit of capacitor, capacitor charge equations.
Known concepts of basic electrical engineering will help understand what it is and how one of the basic elements of electrical engineering, electronics and especially - capacitor. The arrangement of two conductors (pads) separated by a thin dielectric layer (i.e., non-conductive material) is called capacitor.
Applying a voltage across the capacitor causes the accumulation of charges q on the lining assembly , the value of which depends on the surface area of the plates and the distance between them. The larger the charge q accumulated in the capacitor when the voltage U, the greater is the capacitance C.
The capacitance is directly proportional to the surface plate of a capacitor and the dielectric permittivity ε, and inversely proportional to the distance between the pads.
Characteristic of the capacitor is like the concentration of the electric field between the plates. Thanks to the external body and the field does not affect him. Placing the dielectric in the electric field causes the Coulomb potential:
- cause a shift of charged body as a result of deformation of symmetric molecules of the dielectric
- rotate unbalanced molecules
E field inside the dielectric determines the external field E 0 (the field in the absence of dielectric), and the average value of E Wed microscopic fields produced by the dielectric polarization charges. In the condenser field polarization it is opposite to the direction to the field of incident and for most dielectrics it is proportional to its value (χ - electric susceptibility of the dielectric)
Since E = E 0 + E Wed is
Member (1 + χ) indicates how many times the intensity of the field without dielectric is greater than the dielectric, ie. It represents a relative permittivity ε r , which was mentioned by almost Coulomb.
In the system of SI in order to characterize the field without dielectric uses the concept of electric induction vector D, which does not depend on the electrical properties of the dielectric material as it is characterized by the absence of the dielectric field. It is determined only by the arrangement of cargo producing field. A stream of this vector (schematically - the number of lines of force) by the closed surface S is equal to the sum formula of the cargo contained within the surface. Again, unfortunately, the best explanation of this integration (indefinite integral)
Of course there is also equality:
D = ε * E = ε 0 * ε r * E
Polarization density is caused to increase after the capacitor dielectric between the plates of a capacitor. This is because its introduction causes a decrease in field strength, which in turn causes the voltage drop between the pads. Because C = Q / U, the capacity increases in proportion to the value of ε.
Capacitors can be combined to obtain a specific, required capacity. Basically, there are two ways to connect the capacitors: serial and parallel. The so-called. combining the mixed combination of the two. The figures below show combining capacitors.
With parallel connection the resultant capacitance of the capacitor bank equal to the sum of their capacity:
C in = C 1 + C 2 + ... + C n
When connecting serial resultant capacitance of the capacitor bank is:
1 / C a = 1 / C 1 + 1 / C 2 + ... + 1 / C n
The unit of capacitance is the farad (F)
The polarity is usually marked by printing the character "-" on the foil coating housing - should not, therefore, its a rip off! Frequently legs new capacitors have different lengths. Then longer a plus , and the shorter minus. Reverse connection capacitor pole can threaten its damage, and even a short circuit or explosion !
A non-polar capacitor is very much, and their differentiation results from the materials that are used for dielectrics between the covers. It is used, inter alia:
ceramic (ceramic capacitors)
films (capacitors, polyester and polypropylene)
Each group has different applications. Capacitors ceramic used in high frequency circuits.
Capacitor foil in systems operating at voltages due to the high tensile strength (of the order of hundreds of volts) and a small loss. Electronics which is based on microcontrollers (as well as most digital circuits),enough ceramic capacitors.
capacitors, depending on the embodiment, are also present in various housings.Ceramic can be found as small, brown "pills" - this can be found in the kit . Foil in turn are known as the rectangular cubes in different colors.
There are also capacitors tantalum , which combine the advantages of the electrolytic capacitor (large capacity) and ceramic (no drying, low loss), but they are not widespread among beginners because of the relatively high prices. Probably you will be used when you start to build more complex devices.
In the case of tantalum capacitors colored stripe on the body indicates positive terminal! If these elements Mount the opposite way will cause a short circuit !
This is the limit , so you must use capacitors for voltages higher than those which are anticipated in the system. Most voltages are: 10V, 16V, 25V, 35V, 50V, 63V and 100V.
For example, a system powered by a car battery voltage (typically 12.8, up to 14.4V or 15V than the defective charging system) can be used capacitors, voltage 16V, but remain very small margin. You can use a capacitor adapted to the voltage of 25V.
There is no clear answer to the question of how much greater will be the operating voltage of the capacitor predicted that it occurs on the job. It is often assumed, at least 20% above the maximum expected supply voltage.
Some electrolytic capacitors with small capacities, as 1μF or 2,2μF are manufactured for voltages 50V and larger. There are no contraindications to use them in systems powered by voltages of a few volts.
