Fixed vs Variable Capacitors: What’s the Difference?


Batteries aren’t the only devices that are capable of storing energy. Capacitors can store energy as well. A capacitor is a small device that’s designed to store electrical energy in the form of an electric field. They are commonly found in power supply units, air conditioning systems, appliances, lighting systems, fans and more.

Most capacitors can be classified as either fixed or variable. Both types of capacitors are designed to store electrical energy in the form of an electric field. Fixed and variable capacitors, however, aren’t the same.

What Are Fixed Capacitors?

Fixed capacitors are characterized by the use of a nonadjustable capacitance. Some fixed capacitors are polarized, whereas others are non-polarized. Regardless, fixed capacitors have a static, fixed capacitance. You can’t adjust the capacitance of a fixed capacitor.

Capacitance is a measurement of how much electrical energy a device can store. The capacitance of a fixed capacitor can’t be adjusted. They are known as “fixed capacitors” because they have a static, fixed capacitance.

What Are Variable Capacitors?

Variable capacitors are those that feature an adjustable capacitance. You can change their capacitance.

Variable capacitors can be further broken down into several subtypes. Trimmer capacitors are used in radio frequency (RF) applications, whereas tuning capacitors are used to resonate frequencies. These are just a few examples of variable capacitors. There are many subtypes of variable capacitors, all of which feature an adjustable capacitance.

Differences Between Fixed and Variable Capacitors

Fixed and variable capacitors aren’t the same. Fixed capacitors feature a nonadjustable capacitance, whereas variable capacitors feature an adjustable capacitance. You can only change the capacitance of variable capacitors.

Fixed capacitors are far more common than variable capacitors. Most capacitors are classified as fixed capacitors. Variable capacitors have fewer applications, making them more restrictive and less common than their fixed counterparts.

Whether fixed or variable, you can find capacitors in different materials. Some of them are made of ceramic. Other capacitors are made of plastic with a film foil.

How do you know whether a capacitor is fixed or variable? Many manufacturers include symbols on their capacitors. Because they are the most common type, fixed capacitors may not be given a symbol. Variable capacitors, though, can be identified by their unique symbol. The symbol for variable capacitors consists of two vertical and parallel lines with a diagonal arrow running through them. If you come across a capacitor with this symbol, it’s safe to assume it’s a variable capacitor.

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