ABSTRACT
The unit of capacitance, the farad, is a large unit; practical capacitors have capacitances in microfarads, nanofarads, and picofarads. Generally, capacitance is inherent wherever an electrostatic field is present. In many electronic systems, it is necessary to deal not only with the capacitances that are designed consciously within the circuits but also with the unwanted interference and the stray capacitances that are introduced externally or internally at various stages of the circuits. Capacitances can also be expressed in terms of dielectric properties currents and voltages. Bridges are used to make precise measurements of unknown capacitances and associated losses in terms of known external capacitances and resistances. The most commonly used bridges are series RC bridge, parallel RC bridge, Wien bridge, and Schering bridge. An improved version of the series RC bridge is the substitution bridge, which is particularly useful to determine the values of capacitances at radio frequencies.
