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As per the capacitor definition, a capacitor is a component that is able to store electric energy and produce a potential difference in its plates. It is like a small battery that is rechargeable. There is a variety of capacitors available, such as small capacitor beads that are used in resonance circuits and large power factor correction beads. However, all these different kinds of capacitors perform the same function – that of storing energy. Basically, a capacitor is made of two or more plates that are conductive in nature. However, these plates are not connected and do not touch each other.
Capacitance
Capacitance can be defined as the potential of a capacitor to hold electric energy. It is measured in farads. The unit is named after Michael Faraday, who was a British physicist. We can define capacitance as when a capacitor can store a charge of one coulomb to develop a 1-volt potential difference. The value of capacitance can be found printed on the body of a capacitor in the form of a number or text. However, we use pico-farads, nano-farads, and micro-farads to measure capacitance because farad is a very big unit.
Capacitor work
A capacitor works in a somewhat similar way as a battery does. Both a battery and a capacitor store electrical energy. First of all, a metal contains the same amount of positively and negatively charged particles, and that is why it is electrically neutral. When we connect a battery or any other source of power to a capacitor, a current will start to flow. Or we can say that the electrons from the part that is connected to the positive lead of the battery would start to flow to the negative lead of the battery. Capacitors have dielectric mediums between their plates, and this prevents the electrons from passing through the plates. As a result, the electrons would be accumulated on the plates.
When a specific number of electrons have been accumulated on the plate, then the battery will be unable to store new electrons because there is already a sufficient number of electrons present on the plate. The capacitors are completely charged at this point. Now a net negative charge has been developed on the first plate and an equivalent net positive charge is developed on the second plate. This charge will create an electric field and a force of attraction will exist between the plates and the charge of the capacitor will be held by it.
Determine the value of capacitance
Capacitance is the capacity or the potential of a capacitor to hold an electric charge in it. The charge that is accumulated in the capacitor is directly proportional to the voltage developed in it.
C=Q/V
C denotes capacitance, V denotes voltage while the charge is represented by Q.
The physical features of a capacitor determine the value of its capacitance – the area of the capacitor, the distance between the plates of the capacitor, and the dielectric medium’s permittivity.
C= ε A/d
Question 1: There is a parallel-plate capacitor that has two plates. The total surface area is 200 sq cm. Find out the capacitance of the capacitor in pico-Farads when the distance between the plates is 0.2 cm and air is used as a dielectric medium.
Solution: C= ε A/d, ε= 8.85pF/m
A = 100cm2 = 0.01m2, d = 0.2cm = 0.002m
C = 8.85 * 10-12 * 0.01/ 0.001 = 44pF
Factors that affect the capacitance of a capacitor
Surface area: The value of capacitance is affected by the surface area of the plates. The capacitance increases with an increase in surface area.
Distance: The distance between the plates also affects the capacitance, it decreases with the increase in distance and vice versa.
Dielectric medium: The material that is used to separate the two plates in the capacitor is known as a dielectric medium. It could be an isolated medium or just air. The capacitance of the capacitor increases with the increase in dielectric permittivity.
Conclusion
It can be concluded that capacitors are small devices or components that are used to store electrical energy. A capacitor works almost like a battery does and that is why capacitors are also known as small, rechargeable batteries. These are used in a variety of electronic devices and circuits. Capacitance is the capacity of a capacitor to hold electricity. It is printed on the body of a capacitor. It is measured in Farads. However, nano-farads, micro-farads, and pico-farads are used to measure the capacitance. We can use different formulas to determine the value of capacitance.
