Unit of Capacity

The unit of capacity is the capacity of a condenser, in which unit charge produces unit difference of potential between the plates.

The CG.S. unit thus obtained is, however, found to be far too great for practical purposes, and for these the 'farad' has been adopted as the practical unit of capacity. The farad is the capacity of a condenser in which a charge of one coulomb - that is, the charge produced by an ampere of current flowing for one second - is required to produce between the plates of the condenser a difference of potential of 1 volt.

Since the quantity of electricity conveyed by an ampere in one second is 10^-1 C.G.S. units and 1 volt=10⁸ C.G.S. units, we have

Even this capacity, 1 farad, is very large, and it is found more convenient in practice to measure capacities in terms of the millionth part of a farad or a microfarad.

Thus 1 microfarad = 10^-15 C.G.S. units.

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