two conductors that are insulated from each other and placed close to form a capacitor.
conductors forming a capacitor charge equal in magnitude and opposite charges.
widely used in practice is a flat capacitor consisting of two parallel metal separated by a dielectric layer.The distance between the plates is small compared to their size.The capacitor plates are referred to as capacitor plates.
To charge the plate equal opposite charges, you can attach them to the poles of the electric machine.Then on one plate goes negative charge on the other - a positive charge.
You can connect one of the plates of the machine with a pole and the other to ground;while on the other plate by induction there a charge equal in magnitude and opposite in sign to the charge of the first plate.If the plate and the charge is positive, the plate in the induction of negatively charged;The positive charge is neutralized by the electrons in the plate, the plate pritekshimi on the ground, which is a virtually inexhaustible source of them.Attracted to the positively charged plate A negative charge is placed on the inner surface of the plate facing the
A. If A is negatively charged plate, the free electrons are repelled from the plate in the plate A and goes into the ground, with the plate in the chargingpositive.
In both cases, the charges are only focused on the facing surfaces of A and B.
absence of charge on the outer surfaces makes it possible to fully charge the capacitor to pass through the outer sides of the plates.The charge of the capacitor is determined by the charge of one of his plates, as in the other by induction there is equal in magnitude to the charge.
Connect one capacitor plate with the rod of the electrometer, and the other plate and the body of the electrometer grounded.With the ball probe will pass capacitor charge sequentially in equal portions.We note that by increasing the charge in the 2, 3, 4 or more times, respectively, in two, three, four or more times the potential difference of the capacitor increases.
This value, which is measured by the ratio of the charge the capacitor to the potential difference of its plates (or plates) is the capacitance of the capacitor.
denote it by the letter C, you can write:
C = q / (φ1 - φ2).
electric field is concentrated between the capacitor plates is practically inside it, so the surrounding body does not affect the capacity of the condenser.
draw experience.Take the plate capacitor consists of two metal plates A and B are fixed on the insulators.
electrometer connected to the plate A plate in the same grounded.A charge plate, the electrometer while noting some potential difference of the capacitor.If approaching the plate B to A, it can be seen that the potential difference plates decreases.
Reducing the potential difference of the capacitor plates at a constant charge on it indicates an increase in its capacity.
Thus, the capacity of a flat condenser will be the greater, the smaller the distance between the plates is less than either the thickness of dielectric enclosed between the plates.
Shifting plate B with respect to A plate up and down, we will change the area of the plates overlap each other.Watching while the readings of the electrometer, we can establish that the larger the area overlapping the capacitor plates, the greater its capacity.The larger the area of the capacitor plates, the greater the charge can focus on them at this equality potentials.
's do another experience.To do this, arrange the plates of the capacitor A and B at any distance from one another, and the plate and the charge.Note
magnitude of the potential difference when air serves as the dielectric.Now place a sheet of glass between the plates or any other insulator;we see that the potential difference them decrease.To raise it to its previous level, you need to add to the plate and the charge.From this it follows that the replacement of the air layer between the plates of a capacitor any other dielectric increases the capacitance.Let
S₀ - capacitance capacitor, when the void between its plates or air, and C - with its capacity dielectric.
section C and S₀, we find the permittivity of the dielectric reversed ze:
reversed ze = C / S₀.
Thus, the larger the dielectric constant of the dielectric, the greater the electrical capacitance of the capacitor.
