Fixed and Variable capacitors; Fixed Capacitors; Variable Capacitors

FIXED CAPACITOR

Fixed capacitor is the capacitor in which capacitor value remains fixed.

In these capacitor capacitance cannot be adjusted. A fixed capacitor is classified according to the type of material used as its dielectric, such as paper, oil, mica, or electrolyte.

These types of capacitors are discussed in earlier post.

VARIABLE CAPACITOR

As clear from its name variable capacitor is one where A variable capacitor is constructed in such manner that its value of capacitance can be varied.

A variable capacitor is similar to motor having rotor & Stator. It consists of two sets of metal plates arranged so that the rotor plates move between the stator plates. Air acts as dielectric in these capacitors. As the position of the rotor is changed, the capacitance value is likewise changed.

àThis type of capacitor is used for tuning most radio receivers. Its physical appearance and its symbol are shown in figure below.

Another capacitor consists of two plates separated by a sheet of mica. A screw adjustment is used to vary the distance between the plates, thereby changing the capacitance.

Trimmer capacitor.

For knowing about types of Capacitors Visit link below:-

http://electrialstandards.blogspot.in/2015/05/types-of-capacitors.html

To Know about Series and parallel operation of capacitors Visit link:-
http://electrialstandards.blogspot.com/2015/05/capacitor-in-series-and-parallel.html