What is capacitors and capacitance | 2021 | physics | class 10 and 12

A capacitor is a device that stores electrical energy in an electric field. It is a passive electronic component with two terminals.

The effect of a capacitor is known as capacitance. While some capacitance exists between any two electrical conductors in proximity in a circuit, a capacitor is a component designed to add capacitance to a circuit. The capacitor was originally known as a condenser or condensator. This name and its cognates are still widely used in many languages, but rarely in English, one notable exception being condenser microphones, also called capacitor microphones. Connecting two parallel circuits together can add capacitor capacitance, and in most circuits it is used to regulate voltage. A capacitor that is connected to a voltage supply and insulated from the ground uses its capacitance to increase the voltage across the wires while lowering the voltage at each conductor. Diagram of how a capacitor works Disadvantages of a capacitor The main disadvantages of capacitors are Low voltage/current density of the capacitor can lead to interference when high currents are drawn, making the circuit unusable Capacitors use a lot of energy. Their capacitance depends mainly on the voltage and current density in the circuit. If a high current is drawn and voltage is not increased then energy will be lost. This is often indicated as the voltage dropping below the minimum voltage or even breaking into a sudden and irregular energy transfer. The energy lost may be equal to some or more than the capacitance, and this can lead to permanent damage or damage to other components. At high voltage or current densities capacitor is not much useful. Capacitance is not a very good energy store for a capacitor, in the case of a capacitor that is consumed most of the stored energy will be consumed. The high energy consumption in the capacitor may be due to high temperatures, or high energy density of the heat generating components. Capacitors with low voltage/current density may be more resistant to high temperature. However, to make a capacitor that has low voltage/current density it needs a higher voltage across the voltage receptors. So the capacitor may have lower energy densities compared to capacitors with high voltage/current densities. Figure 5. A capacitor that is not necessarily representative of typical capacitors Figure 6. A capacitor with low energy density and low voltage/current density and not necessarily representative of typical capacitors If a capacitor is damaged, then the current and voltage have to be increased to compensate for the reduced capacitor capacitance. Sometimes damage can be so severe that electrical traces will be completely melted, even to the point where energy will not be dissipated by a current that would be dissipated if not damaged. An improved capacitor with low voltage/current density and low energy density Over time, capacitors can become almost totally depleted of energy. This can lead to failure of the circuit or damage to other circuits. There are devices which allow this very easily. These devices have low voltage and high current densities. These capacitors allow for the amount of energy that can be stored to be increased by some means, such as electrical damping. One particular type of capacitor is the capacitor plug, which is designed to reduce the voltage across a terminal on the capacitor and limit current flow. A capacitor plug using multiple converters to reduce voltage to low and then to increase voltage. A capacitor plug using a single capacitor plug.

Connecting two or more parallel circuits is a great way to make a capacitor with high voltage and low current density. Usually this connection is made in the middle of the circuit, although a capacitor plug may be connected directly between two parallel circuits.

Bipolar capacitors

Bipolar capacitors have two terminals and have different capacitance values across them. In a bipolar capacitor the voltage at one terminal increases, and the voltage across the other terminal decreases.

Figure 7. A bipolar capacitor is a capacitor that has two different energy levels.

A bipolar capacitor works similarly to a capacitor with a lower voltage. However the difference is that the voltage across the first terminal is high and the voltage across the second terminal is low. Because of this high voltage across the first terminal and low voltage across the second terminal the capacitor stores much more energy.

If a capacitor has a voltage between these two terminals then most of the energy stored