What are Capacitors and their History? Conventional capacitors are a passive device which stores electric energy in the form of static electric field. It consists of two plates that is called electrodes and these electrodes are separated by an insulating layer. When it is connected with a battery or any energy source then positive charges are added up at positive electrode and negative charges are added up at negative electrode but both charges could not mix up due to insulating layer. Now if we remove the energy source then electric field would be always present at electrodes plates unit both electrodes are shorted through a conductor. When it is shorted through a conductor then current flows in this specific conductor at that time until potential difference of both plates is same. This one is the basic working phenomena of a capacitor. Working phenomena of every capacitor is same but they are available in market in different types and sizes. you may also like to check types of inductors.
These types and sizes are based on their voltage level and value of capacitance. First time capacitor was invented by Pieter van Musschenbroek in 1746, who was the professor in Holland in university of Leyden (or Leiden). That time, the name of invented capacitor was Leyden jar, which was made up with the help of a glass jar. For making the capacitor of this glass jar he wrapped a thin metal foil inside and outside of this glass jar then he connected the outer side of this jar to a ground and inner side to the energy source such as generator. Even, that time he was not know how it would be work, he did so many experiments on this, but he could not get any results. At the end mistakenly when he picked up the jar then he suddenly felt the heavy electric shock then he understood he have discovered a capacitor. That time this glass jar had been used as a capacitor but later on after so much research a proper shape of the capacitor has discovered. This was the brief history of capacitor. Now the capacitor has become the most commonly used component in electronic circuits. It plays an important role in electronic design circuits and embedded system applications. Different capacitor symbols such as fixed capacitor, variable capacitor and polarized capacitor symbols are shown in figure
Different Types of Capacitors
Capacitor is a very significant component in electronic devices. They are manufactured in millions quantity on daily biases but there are so many types of capacitors are available in market. Each type has its own advantages and disadvantages but a little much knowledge about these capacitors is necessary for the user so that they can choose the correct one for any special purpose application.
- Electrolytic Capacitors: It is the type of capacitor which are mostly polarized capacitors and they are widely used in that palaces where high value of capacitance is required. Normally in some places thin film metallic capacitors are used which consist of only single electrode but at places semi liquid electrolytic capacitors are very suitable solution which are available in the form of jelly or paste which works as second electrode. Because it consists of a thin layer of oxide material which grown electro chemically in less than ten microns with the thickness of film therefore when it is used in circuit or anywhere then must care about its polarity. Means negative terminal is connected with negative power supply terminal and positive terminal is connected with positive power supply terminal otherwise its opposite polarity will damage the insulation oxide layer means it will damage the capacitor permanently. These capacitors are operated at DC power supply and are available above from 1micro farad. A simple electrolytic capacitor is shown in figure 2
Figure 2 Simple Electrolytic Capacitors
- Ceramic Capacitors: Ceramic capacitor is a type of capacitor which are made up with ceramic or porcelain material. The physical shape of these capacitor is such like a disc therefore these are also known as disc type capacitor. Because it has very low capacitance value therefore the physical size of these capacitor is mostly 3 to 6 mm. It has high dielectric strength constant (HIGH-K) therefore a high value of capacitance could be merged in a small size. Its capacitance does change with temperature therefore they are used as de-coupling or by pass capacitor and these are non-polarized capacitor. These are available in market in the range between Pico farad to one or tow micro farad. They are mostly used in audio and RF applications. They are less costly more reliable, and their loss factor is relatively less as compared to other capacitors. A simple ceramic capacitor is shown in figure 3.
Figure 3 Simple Ceramic Capacitors
- Tantalum Electrolytic Capacitors: Tantalum electrolytic capacitors are also polarized capacitor just like an electrolytic capacitor and they offer a very high level of capacitance value. Its behavior is very intolerant during revers biased condition and they cannot bear high voltage or ripple current above their certain level. They are easily available in market in both formats such as in leader and surface mount format. However, some types of tantalum capacitor contain two capacitors in a single body and in these types negative terminal is connected to a negative power supply to form a non-polarized capacitor which are mostly used in low voltage ac circuits. Similarly, the positive terminal is marked at capacitor body and the overall shape of this capacitor is just like a geometry. Its typical values are available between the range 47nF to 470uF. A simple tantalum electrolytic capacitor is shown in figure 4
Figure 4 Simple Tantalum Electrolytic Capacitors
- Variable Capacitor: It is the type of capacitor whose capacitance values could be changed by the user intentionally by moving the knob of the capacitor mechanically. These types of capacitors are mostly used for set the resonance frequency in LC filter circuits and they are also used signal processing devices, energy storage systems and motor starter systems. A simple variable capacitor is shown in figure 5
Figure 5 Simple Variable Capacitors
- Silver Mica Capacitor: It is the type of capacitor which are not mainly used but they still offer high level of stability, low loss and high accuracy where space is not an issue. They are mostly used in RF applications, but they are available in limited values such as 1000 pF and so on. Their cost is so much high as compared to other type of capacitors. Some simple silver mica capacitors are shown in figure 6
Figure 6 Some Simple Mica Capacitors
- Polystyrene Film Capacitor: It the type of capacitors which are very cheep as compared to other type of capacitors, but they offer close tolerance capacitor where there is needed. They offer tolerance near about 5% to 10% which is suitable in many applications. They are available in the form of leader electronic components. Some simple polystyrene film capacitors are shown in figure 7
Figure 7 Some Simple Polystyrene film capacitors
- Glass Capacitor: In glass capacitors, glass is used as a dielectric material. They offer high level of working performance, low loss and high current carry capability but they are so much costly as compared to other types of capacitors, A simple glass capacitor is shown in figure 8,
Figure 8 Simple Glass Capacitor