Brief History

In this material, let us know the history of capacitors. In the month of October in 1745, German Ewald Georg von Kleist of Pomerania noticed that charge can be collected in a specific amount of water in a handheld glass jar connected to a high-voltage electrostatic generator with the help of a wire. Von Kleist felt that touching the wire generated a strong spark that was far more powerful than the electrostatic machine’s. Von Kleist believed that his hand and water served as conductors, while the jar served as a dielectric (however, the actual working of the mechanism was falsely noted at the time). 

Later on, Pieter van Musschenbroek, a Dutch scientist, constructed a capacitor which was similar to that of Ewald’s and called it Leyden jar. The name was given after the University of Leiden, where he used to work.

Daniel Gralath, a physicist and the mayor of Danzig at the time, combined a group of jars in parallel to improve the charge storage capacity. Later on, Benjamin Franklin explored Leyden jar and came to the conclusion that the charge was actually stored in the glass and also named the group of Leyden jars as “Battery”.

In the later period, in order to stop the arcing between the foils, Leyden jars were manufactured by covering the inside and exterior of the jars with metal foil and leaving a space at the mouth. The first capacitance unit that was recorded for the jar was equivalent to around 1.11 nanofarads.

Until around 1900, when the wireless (the radio) was introduced, it formed a quick requirement for standard capacitors. Most of the devices used Leyden jars that were made using plain glass plates wrapped with foil conductors, which were used predominantly. Later on, more compact construction methods, such as a flexible dielectric sheet (which seems like oiled paper), which were squeezed between sheets of metal foil and rolled or folded into a small package, began to be used.

In the initial period, the early capacitors were named condensers, and the term is still used infrequently today, especially in high-power applications like automobile systems. However, Alessandro Volta came up with the term “capacitor” for this purpose in 1782, referring to the device’s capacity to store a higher density of electric charge as compared to an isolated conductor. Due to the unclear interpretation of steam condenser, the term was discontinued, and capacitor became the preferred term in 1926.

As from the commencement of the study of electricity, non-conductive materials such as glass, porcelain, paper, and mica have been widely used as insulators. These materials were used as dielectrics when capacitors were initially used. Paper capacitors, which were made by layering a strip of impregnated paper in the middle of the strips of metal and rotating into a cylinder, were widely used in the late 19th century. Industrial production of such capacitors began in 1876, and they were used as decoupling capacitors in telephone services from the early 20th century. 

The very first ceramic capacitors were made of porcelain. Porcelain capacitors were utilised in the initial years of Marconi’s wireless transmitting gear for high voltage and high-frequency applications in the transmitters. At the time of World War II, organic chemists developed plastic materials, and the capacitor business replaced paper with thinner polymer sheets. In 1944, British Patent 587,953 documented an early development in film capacitors.

Working of a Capacitor

A capacitor is developed with the help of two conductors that are kept apart with the use of a non-conductive region. This region can be filled with an electrical insulator, therefore, a dielectric or with a vacuum. A few of the examples of dielectric material are air, paper, glass, ceramic, etc.

According to Coulomb’s law, the charge on one of the two conductors will exert a force on the carrier in the other. This will attract the charges of opposite polarity and repel the charges of similar polarity. This will result in a positive charge on this conductor, while a negative charge on the other conductor will be generated. Thus, the conductor holds equal and opposite charges on both of its surfaces, and the dielectric develops an electric field. 

 The ideal capacitor is characterised by a constant capacitance C, in farads in SI units, which can be determined by the ratio of the positive or negative charge Q on each conductor to the potential difference V between them.

C = QV

One farad (F) capacitance means that a capacitor charge on each conductor causes a voltage of one volt across the device. Since the conductors (or plates) are in close proximity, opposite charges on the conductors attract due to their electric fields, allowing the capacitor to store more charge for a given potential difference. When the conductors are far apart, the power is greater.

Conclusion

Regarding the history of capacitors, German Ewald Georg von Kleist came up with the very initial idea of the capacitor in October 1945. Later on, Pieter van Musschenbroek came up with a Laden jar; these jars were grouped together by Daniel Gralath. In the latter period, Benjamin Franklin explored the Laden jar and came up with the term “battery”. The name of the capacitor in the initial period was conductor, which was discontinued, and capacitor became the preferred term in 1926.