If a voltage is applied between the plates, the capacitor takes a certain charge depending on the size and distance of the plates and the dielectric between them. The charge is proportional to the voltage, and the ratio of charge to voltage is called capacitor capacitance (see this). The capacitance of a capacitor consisting of two parallel plates with area S , separated by a dielectric of thickness d and permittivity ε is equal to ε · S / d . Thus, the capacitance increases when using a dielectric with high permittivity. Between the plates in a capacitor there is an electrostatic field. When condensing and discharging the capacitor, some of the energy in the field passes to heat in the dielectric. This is called dielectric loss (**Class y capacitors**).

If the plates are subjected to an alternating voltage , the capacitor will be charged and discharged as the voltage increases. The capacitor seems to flow through it. In reality, in one part of the period it occupies a charge that it returns to the next part. The current is maximum when the capacitor has no charge, that is, when the voltage above it is zero. There is a phase difference so that the flow is 1 / 4 period before the voltage. By alternating currents through inductances , current is after voltage and the capacitor is therefore used as phase compensator to reduce the phase shift occurring in an AC power grid due to the fact that there are connected inductors, for example in motors (**Class y capacitors**).

For connection of capacitors , see parallel connection and serial coupling .

## Use

Electrical capacitors are important components of electrical instruments, filter circuits and amplifiers , and have many applications in telephone and radio technology , measurement technology and so on.

## Series connection of capacitors

- A series connection of capacitors is given when the same alternating current or charging / discharging current flows through all the capacitors. Note: Capacitors allow only alternating currents or charge / discharge currents to flow.
- The series connection causes a reduction in capacity, comparable to an increase in the plate spacing with the same plate area.
- Sometimes the series connection is also called series connection. No matter how, the capacitors are always connected in series.
- Often, a calculated capacity is not available as a capacitor. Instead, two or more capacitors are connected in series to get the calculated value.
- At high voltages, several capacitors are connected in series to prevent the risk of breakdown. It is helpful that the total voltage is divided at the capacitors.

**Behavior of the voltages**

The total voltage U ges is shared by the capacitors in the series connection. The sum of the partial voltages is equal to the total voltage. At the smallest capacity, the greatest voltage drops. At the largest capacity drops the smallest voltage.

**Behavior of the capacity**

The total capacity of the series connection is smaller than the smallest individual capacity. Each additional series capacitor reduces the total capacity.

**Behavior of the charges**

- The charges of the capacitors are the same size.
- Series connection of two capacitors
- If only two capacitors are connected in series, then the equation for calculating the capacitance can be simplified.

## Parallel connection of capacitors

- A parallel connection of capacitors is given when the current is divided at the capacitors and applied to the capacitors the same voltage.
- At point A the current splits and at point B it flows together again. Between point A and point B, the total voltage is applied. Note: Capacitors allow only alternating currents or charge / discharge currents to flow.
- Capacitors are very often connected in parallel to increase the capacity. A variable capacitor consists z. B. from parallel capacitors.

**Behavior of the voltages**

In the parallel connection of capacitors, the same voltage is applied to all capacitors.

**Behavior of the capacity**

As the current charges the capacitors, the total capacitance of all capacitors is greater than for each individual capacitor. The total capacity is equal to the sum of the individual capacities.

**Behavior of the charges**

The charge behaves the same as the capacity. The total charge is equal to the sum of the individual charges.