A capacitor is an element that stores energy in the form of an electrostatic field. It is denoted as "C" and it is measured in Farads (F). A capacitor is a passive component consisting of a pair of conductors separated by a dielectric. When a potential difference exists between the conductors in the capacitor, an electric field will be present in the dielectric.
They are used in resonant circuits in radio frequency equipment to select a particular frequency signal from signals with many frequencies. The charge storage ability of a capacitor is called the capacitance of a capacitor.
Features of Capacitors and Capacitance
A capacitor is said to have a capacitance (C) of 1 Farad if it stores a charge (Q) of 1 coulomb when a voltage (V) of 1V is applied across its plates. Therefore, the capacitance of a capacitor can be mathematically expressed as:
Capacitance = Charge / Voltage Farads (i.e. C = Q / V Farads)
The plates or foils of a capacitor can be of any size and shape and the dielectric may be any one of several insulator materials. Depending on the type of insulator/dielectric used, capacitors are called paper, mica, ceramic, glass, polyester, air electrolyte capacitors, etc.
Capacitor Charging and Discharging
The following media shows the charging and discharging of a capacitor in D.C. circuits.
Capacitance of a Capacitor
The capacitance of a capacitor is determined by the following three main factors:
- Area of the plates
- Distance between the plates
- Type of dielectric material
In addition to the above factors affecting the value of capacitance, the temperature of the capacitor also affects the capacitance although not very significantly. Some dielectrics cause an increase in capacitance as temperature increases. These are called positive temperature coefficients.
Colour Coding of a Capacitor
Like resistors, the capacitance value of the capacitors can also be identified by colour coding. Nowadays in most capacitors, like electrolyte capacitors, the capacitance value is printed on the body of the capacitor in the form of alphanumeric characters.
The colour-coding method is mostly applied to disc type, ceramic, and mica capacitors. The colours are printed on the top of the capacitor.
Color Coding of Capacitors
The following media explains the colour-coding of capacitors.
Question: Which of the following formula can be used to determine the resistance value 'R' if the power factor angle and the impedance value (Z) of a circuit are known? Choose one and write the answer in the comment section below.
- R=ZSin0
- R=ZCos0
- R=Z/Cos0
- R=Z/Sin0
Write your answer in the comment section below.
