Important differences between Fixed capacitor & variable capacitor

Here we will discuss differences between fixed and variable capacitor. How they are different, how to use them and also what are the different scenerios where they will be used.

What is Capacitor ?

Capacitor is a charge storing device which is made of different components like anode and cathode. In between those two plates there will be insulating material which is used to hold the charges separated on electrodes.

The capacitor plates will be either separated by “air” or “Dielectric” materials. The charge will be stored in between two electrodes.

How a Capacitor works ?

In general perspective we know that fixed capacitor will be storing fixed amount of charge and variable capacitor will is capable of storing variable amount of charge. For example, if a capacitor is designed to store 10 micro farad of charge then it will be only storing charge 10 mivro farad or less than that charge. But if it’s variable capacitor then it’s capacitance will be changing.

How Variable Capacitor works ?

We know that amount of charge stored in a capcitor will be depending on the amount of distance between two electrodes. If the distance is less then the amount of charge stored in capacitor will be less. But if the distance between two electrodes is less than amount of charge stored will be less.

Ultimately we can say that if the distance between electrodes increases then charge storing capacity increases.

Alright now the point is that variable capacitor will be having three nodes, two nodes will be fixed and third variable is adjustible, so

• If we rotate 3rd notch in clockwise direction the distance between electrodes increases, then charge storing capacity also increases.
• If we rotate 3rd notch in Anti-clockwise direction the distance between electrodes decreases, then charge storing capacity decreases.

Types of capacitors

There are maily two types of capacitors as mentioned below

1. Fixed capacitor
   1. paper capacitors
   2. plastic capacitors
   3. ceramic capacitors
   4. Mica capacitors
   5. Electrolytic capacitors
2. Variable capacitor
   1. Tuning capacitor
   2. Trimmer capacitor

There are couple of differences between fixed and variable capacitors in terms of charge storing capacity and physical structure of the capacitors.

Difference between fixed and variable capacitor

Fixed Capacitor	Variable Capacitor
They can store fixed amount of charge	They can store variable amount of charge
Generally will be having only 2 pins	Generally will be having 3 pins
The distance bwteen electrodes will be fixed	The distance between electrodes is variable
Cheaper compared to variable capacitor Used in charging circuits	Costlier compared to fixed capacitor Used in Radio frequency generating circuits
Easy to manufacture and simple	Difficult to manufacture and Complex

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