Capacitors
A Capacitor is a passive component that has the ability to store the energy in the form of potential difference between its plates. It resists a sudden change in voltage. The charge is stored in the form of potential difference between two plates, which form to be positive and negative depending upon the direction of charge storage.
A non-conducting region is present between these two plates which is called as dielectric. This dielectric can be vacuum, air, mica, paper, ceramic, aluminum etc. The name of the capacitor is given by the dielectric used.
Symbol and Units
The standard units for capacitance is Farads. Generally, the values of capacitors available will be in the order of micro-farads, pico-farads and nano-farads. The symbol of a capacitor is as shown below.
The Capacitance of a capacitor is proportional to the distance between the plates and is inversely proportional to the area of the plates. Also, the higher the permittivity of a material, the higher will be the capacitance. The permittivity of a medium describes how much electric flux is being generated per unit charge in that medium. The following image shows some practical capacitors.
When two plates having same area A, and equal width are placed parallel to each other with a separation of distance d, and if some energy is applied to the plates, then the capacitance of that parallel plate capacitor can be termed as −
C=ε0εrdAC=ε0εrdA
Where
C = Capacitance of a capacitor
ε0ε0 = permittivity of free space
εrεr = permittivity of dielectric medium
d = distance between the plates
A = area of the two conducting plates
With some voltage applied, the charge deposits on the two parallel plates of the capacitor. This charge deposition occurs slowly and when the voltage across the capacitor equals the voltage applied, the charging stops, as the voltage entering equals the voltage leaving.
The rate of charging depends upon the value of capacitance. The greater the value of capacitance, the slower the rate of change of voltage in the plates.