What is capacitance? Electric capacitance is the ability of a conducting body to accumulate charge. The capacitance value of a capacitor is obtained by using the formula: where C is the capacitance, Q is the amount of charge stored on each electrode, and V is the voltage between the two electrodes. In real life circuits the amount of charge on one plate equals the amount of charge on the other plate of a capacitor, but these two charges are of different signs. By examining this formula it can be deduced that a 1 F capacitor holds 1 C of charge when a voltage of 1V is applied across its two terminals. The unit of capacitance The unit of capacitance is a Farad [F]. This unit can be somewhat impractical. From the vantage point of most electrical engineers, one farad is a huge capacitance value. Most electronic circuits use capacitors of only up to a few mF. There are several good reasons for this. One reason is that, when dealing with signals in an electrical circuit, as the frequency of the signal increases, the need for high capacitance capacitors decreases because, at higher frequencies, even a small capacitor can make a big impact on the circuit. Since most modern digital circuitry has a tendency to move towards higher frequencies in order to meet demands for improved processing speed, these circuits mostly use capacitors of only up to a few mF. As a result, the need for large capacitors is virtually non-existent in the signals processing parts of electrical circuits. Another reason is that high capacitance capacitors are physically large. Therefore, the use of such capacitors is avoided, especially in mobile devices. However, there have been recent technology advances in the field of supercapacitors. Thanks to these advances, it is now possible [… read more]