What is a Capacitor Polarity : Construction & Its Types

A capacitor is an electronic component, that stores energy in electric form when charged and is also known as a two-terminal passive component or a condenser, measured in Farads (F). It consists of two metallic parallel plates which are separated by a gap filled with a dielectric medium. They are classified into 3 types they are fixed capacitor, polarised capacitor, and a variable capacitor. Where a fixed capacitor has fixed value of capacitance, a polarised capacitor has two polarities (“+ve” and “-ve”), and in a variable capacitor, the capacitance value can be changed depending on the application. This article gives an overview of capacitor polarity and its types.

What is Capacitor Polarity?

Definition: A capacitor is a passive element that stores a small amount of charge in it. They are classified into two types, one is a polarised capacitor (the capacitor which is specified with its polarity) and another non-polarised capacitor (capacitor whose polarity is not specified). It consists of 2 leads which are represented as an anode (+) and a cathode (-) as shown in the below schematic. If the capacitance of a capacitor has fixed polarity, it is connected based on circuit polarity direction.

Capacitor Equivalent Circuit

An ideal capacitor consists of two metallic plates that are separated by a distance “d”. The gap between the capacitor is filled with a dielectric medium which acts as an insulator. This construction makes the capacitor a perfect capacitor. But in the real world, it is not possible to have a perfect capacitor due to leakage current whenever current flows through the capacitor. Hence we construct an equivalent circuit of a capacitor connecting a series resistor ”R_series “and a leakage resistor “R_leakage ” as shown below.

Capacitor Polarity Identification

The polarity of capacitors can be identified in several ways as follows.

Based on the height of the capacitor leads we can identify which is negative polarity and which is positive polarity. Capacitor whose terminal is longer is a positive polarity terminal or an anode and the capacitor whose terminal is shorter is a negative polarity or cathode.

If the capacitor is not polarised, we can connect it in any direction. We can easily identify if it is non-polarised by viewing the NP and BP mark on the capacitor. For a few capacitors there exist a positive “+” and “-“ symbol on the component.

Capacitor polarity Examples

The examples of capacitor polarity include the following.

Big Capacitor

From the below figure, we can observe a DOT sign near the terminal, which is a positive polarity terminal also known as anode and another terminal is referred to as a negative polarity terminal known as the cathode. Arrow indications on the capacitor are another identification of polarity.

Arrow Representation Capacitor

From the figure we can observe a black color arrow, pointing toward the terminal is a negative polarity terminal.

Types of Non-Polarity Capacitors

The capacitors whose polarity is not specified is a non-polarity capacitor. It can be connected in any way on the Printed Circuit Board (PCB). There are different types of non-polarity capacitors like

• ceramic capacitor
• silver mica capacitor
• polyester capacitor
• polystyrene capacitor
• glass capacitor
• film capacitor, etc.

Among these, the most commonly used capacitors are a ceramic capacitor and a film capacitor.

Ceramic Capacitor

The ceramic capacitor is a constant capacitance value and it is made up of a material called ceramic. It is also known as dielectric material (a dielectric material does not allow current to flow freely through it). Generally, the ceramic capacitor is constructed with many alternating layers of ceramic with a metal layer between them (where metals used in capacitor acts like electrodes). The 2 electrodes present are of positive and negative polarity.

A ceramic capacitor is further classified into two classes, where the class1 ceramic capacitor has high stability and low losses and class 2 ceramic capacitor has high buffer efficiency for volumetric, by-pass, and coupling applications. These capacitors are available in different shapes and sizes. They come under the non-polarised capacitor category, which can be connected in any way on the PCB.

Film Capacitor

A film capacitor is also called a plastic capacitor or plastic film capacitor, polymer film capacitor. They are constructed using 2 plastic films along which metallic electrodes are placed inside a cylindrical winding and encapsulate. They are classified into two types, metal foil capacitor, and metalized film capacitor. The advantage of the film capacitor is its construction and the film material being used. They are non-polarity capacitor category, which can be connected in any way on the PCB.

Electrolytic Capacitor

An electrolytic capacitor is a polarised capacitor, which consists of a cathode and an anode. The anode is a metal, which on anodization forms a dielectric material and the cathode is a solid, liquid, or a gel-type electrolyte that surrounds the anode. This construction makes the electrolytic capacitor to have a very high capacitance-voltage value on the anode. They are used in the areas where the input signal is given is of lower frequency and stores larger energy. It is usually constructed in two ways.

• Aluminium Electrolytic Capacitor
• Tantalum Electrolytic Capacitor.

Electrolytic capacitors are polarised by their asymmetric design. They operate with a voltage higher than the voltage of other capacitors. The polarity is differentiated as “+” which means an anode and “-“ means cathode. If a voltage applied is greater than 1 or 1.5 V then the capacitor breaks downs.

Advantages

The following are the advantages

• Lowers power consumption in circuit
• Occupies less area
• Protects the circuit from being damaged.

Disadvantages

The following are the disadvantages

• Fewer life spans
• If the applied voltage is more than the capacitor capacitance, the capacitor may breakdown
• Is connected in polarity direction
• Highly sensitive to the external environment.

Applications

The following are the application

• Electronic filters
• Half-wave rectifiers and Full wave rectifier
• Multimeters
• Chargers
• Digital memory, etc.

FAQs

1). What is a capacitor?

A capacitor is a device that stores a small amount of charge in it.

2). Classification of capacitors?

A capacitor is classified into 2 types they are polarised capacitor and non-polarised capacitor.

3). Difference between polarised and non-polarised capacitors?

A capacitor whose polarity is labeled on the component is a polarised capacitor. These kinds of capacitors are connected based on the direction of the circuit and a capacitor whose polarity is not mentioned on the component is a non-polarised capacitor. Theses kind of capacitors can be connected in any direction on the PCB.

4). What are the examples of non-polarised capacitors?

The following are the examples of non-polarity capacitors, they are

• ceramic capacitor
• silver mica capacitor
• polyester capacitor
• polystyrene capacitor
• glass capacitor
• film Capacitor.

5). What are the examples of polarised capacitors?

An Electrolytic Capacitor is the best example of polarised capacitors, they are mainly used to provide a large voltage supply.

Thus, a capacitor is an electronic component that stores a small amount of charge in it. They are classified into 2 types of polarised capacitors and non-polarised capacitors. Certain capacitor polarity can be identified by the height of the capacitor, NP and BP mark, “+” and “-“ symbol and arrow indications on the capacitors. Capacitors are mainly used to prevent current leakage in the circuit.