**Capacitors**, **C **are also simple *passive devices*.

The capacitor is a component which has the ability or "capacity" to store energy in the form of an electrical charge producing a potential difference across its plates.

Capacitors consists of two or more parallel conductive metal or foil plates which are not connected or touching each other but are electrically separated either by air or by some form of insulating material such as paper, mica, ceramic or plastic and which is commonly called the capacitors **Dielectric**.

“The material used to separates the plates of a capacitor from each other is called the **Dielectric**”

The symbol used in schematic and electrical drawings for the Capacitor can either be a two parallel lines or a straight and curved line.

A capacitors ability to become charged by a voltage and then hold that charge indefinitely allows capacitors to be used in electrical and electronic circuits in a variety of ways, from smoothing out fluctuations in voltage power supply levels to timing and filter circuits when used in the conjunction with a resistor.

### Capacitor Symbols

When the plates of a capacitor are connected across a DC supply voltage, it takes some time for the charge (in the form of electrons) on the plates to reach their full intensity. When a sufficient amount of charge, **Q **(measured in units of coulombs) have been transferred from the source voltage to the capacitors plates, the voltage across the plates, Vc will be equal to the source voltage, Vs and the flow of electrons will cease.

The voltage developed across the capacitors plates is not instantaneous but builds up slowly at the rate that depends on the capacitance value of the plates, the greater the capacitance, the slower the rate of change of voltage in the plates.

The capacitance, **C **value of a capacitor is an expression of the ratio between the amount of charge flowing and the rate of voltage change across the capacitors plates.

A capacitance of one *farad**, ***F**, represents a charging current of one ampere when there is a voltage, V increase or decrease at a rate of of one volt per second. Then one coulomb of charge exists when a capacitance of one farad is subjected to one volt of potential difference and for a parallel plate capacitor the ratio of **Q ÷ V **is a constant called the capacitance, **C **as shown.

Q = VC, C = Q÷V, V = Q÷C

Where: **V **in volts, **Q **in coulombs and **C **in farads. Note that when **C **is given in microfarads, (μF) and **V **in volts, charge **Q **will be in micro-coulombs (μC).