What is a Paper Capacitor – Construction, Working & Applications

In every electronic circuit, resistors and capacitors are used as a passive component to resist and store electrical energy. Generally, Paper Capacitor is also known as condensers, which is made up of two conducting surfaces separated by an insulating material. This material is called the dielectric. Capacitors offer a low resistance path to A.C voltage and high resistance to D.C voltage from one circuit to another circuit. This capacitance of the circuit is stored in the form of an electric field. It opposes the flow of voltage in any electronic circuit and blocks the flow of direct current passing through it. Capacitors are manufactured with different packages, various types, and values based on the application.

What is the Paper Capacitor?

Definition: Paper capacitor is also known as a Fixed capacitor, in which paper is used as a dielectric medium, that stores energy in the form of the electrical field. These capacitors are used at power line frequency with a capacitance value of 1nF to 1uF. It stores a fixed amount of electric charge.

Working/Function

A paper capacitor is made up of two metallic plates with a dielectric material paper between them. It has positive and negative plates. When a small amount of electric charge is applied over the plates, the positive charge is attracted to one plate and a negative charge is attracted to another plate. This electrical energy is stored in the form of the electrical field. This stored electrical energy is used by the discharging of a capacitor. These are available in the range of 500pF to 50nF. These offer high leakage currents.

Paper Capacitor Values

The capacitance  of the paper capacitor measured in terms of Farad’s(F). The capacitance range of this capacitor varies from 0.001 to 2.000 microfarad with a high voltage range of upto 2000V. Initially, the paper is used between the two aluminum sheets as a dielectric medium. But, now other materials like plastic are also used. These capacitors are available in the range of 300 picofarads to 4 microfarads with a working voltage of 600 volts.

Paper Capacitor Construction

The construction of the paper capacitor is divided into two types.

• Paper sheet capacitor
• Metalized paper capacitor

Paper Sheet Capacitor

The construction of the paper sheet capacitor needs two aluminum sheets and a paper sheet. To protect from the outside environment, the paper sheet is covered with a wax or soaked with oil. Paper capacitors are the fixed capacitors that store a fixed amount of electric charge with a fixed capacitance value. The paper sheet placed between the aluminum sheets acts as a dielectric medium whereas aluminum acts as an electrode.

As the paper is a bad conductor of electricity, it doesn’t allow the flow of electric current between the aluminum sheets, which allows the electric field through it and acts as a barrier of electric current. The paper sheets and two aluminum sheets are rolled in the cylindrical shape and the entire cylinder is coated with wax or plastic resin to protect it from moisture in the air. The two-wire leads are taken from the ends of the two aluminum sheets.

Metalized Paper Capacitor

In a metalized paper capacitor, the paper is coated with a thin layer of zinc or aluminum and rolled in the form of a cylinder. The entire cylinder is coated with wax to protect it from the environment. The metalized paper acts as electrodes and paper act as a dielectric medium. This kind of capacitor coated with zinc can be destroyed easily due to the chemical action. Hence, aluminum is widely used in construction. The size of the metalized paper capacitor is very small when compared to the size of the paper sheet capacitor. Because it has a very thin layer of aluminum when compared to the aluminium used in the paper sheet capacitor.

Applications/Uses

Paper capacitors are widely used in various applications such as,

• High voltage and high current applications.
• used in electrical and electronic applications.
• Power conditioning systems to block DC signals and allow AC signals.
• used in-car audio systems to provide extra power to amplifiers when required
• used as sensors to measure air humidity, fuel levels, and mechanical strain.
• used in electronic noise filtering, signal coupling, and decoupling systems, remote sensing.
• used in signal processing systems such as tune circuits, speakers, dynamic random access memory (DRAM), radio receivers, and analog equalizers.

Advantages & Disadvantages

The advantage of using a paper capacitor is that provides a fixed value of capacitance. The value of the capacitance is fixed during manufacturing.
The main disadvantage is, it absorbs moisture in the air and decreases the insulation resistance of the dielectric. As it absorbs moisture in the air, the dielectric medium is affected.

FAQs

1). What is the Paper Capacitor used for?

A paper capacitor is an electronic device to store electrical energy in the form of an electric field. It is used in various high voltage and high current applications.

2). What is the Symbol of a Capacitor?

The passive electronic component used to store electric charges in the form of the electric field is called a capacitor. The capacitance is measured in Farads. When the capacitor has a larger capacitance, then it has the ability to store more electric charges.

3). What Metal is used in Capacitors?

The plates of the capacitor are made up of conducting material like Aluminum, tantalum, silver and other metals. The dielectric medium is made with insulating materials like paper, glass, rubber, ceramic or plastic depending upon the application.

4). What are the types of Capacitors?

There are 4 types of capacitors. They are,

• Ceramic capacitors
• Film capacitors
• Paper capacitors
• Dielectric capacitors
• Electrolytic capacitors.

5). How do you know if a capacitor is good?

To know the quality of the capacitor, we just need a digital multimeter with a high range and any one type of capacitor that is used in a device.

Connect the multimeter leads to the two ends of the capacitor plates. That is, connect the red lead of the multimeter to the positive plate of the capacitor and black leads to the negative plate. If the reading of the meter starts at zero and moves slowly towards infinity, then the capacitor is good.

Hence using a digital and analog multimeter, the capacitor can be tested to know that it is good or bad or open or short.