There are few theorems that can be applied to find the solution of electrical networks by simplifying the network itself or it can be used to calculate their analytical solution easily.

The electrical circuit theorems can also be applied to A.C systems, with only one difference: replacing the ohmic resistance of the D.C system with impedance.

## Common Terms used in Circuit Theory

- A
**circuit**is a closed conducting path through which an electrical current either flows or is intended to flow. A circuit consists of active and passive elements. **Parameters**are the various elements of an electrical circuit (for example, resistance, capacitance, and inductance).**Linear circuit**– a circuit in which the parameters are constant with time, do not change with voltage or current, and obey Ohm’s law. In a**non-linear circuit**the parameters change with voltage and current.- A
**passive network**is a one which contains no source of EMF. - An
**active network**is a one which contains one or more sources of EMF. - A
**bilateral circuit**is one whose properties or characteristics are same in either direction of current. Example: the usual transmission line is bilateral. - A
**unilateral circuit**is that circuit in which properties or characteristics change with the direction of operation. Example: a diode rectifier can rectify only in one direction. - A
**Node**is a point in a circuit where two or more circuit elements are connected together. **Branch**is a part of a network which lies between two nodes.**Loop**is a closed path in a circuit in which no element or node is encountered more than once.**Mesh**is a loop that contains no other loop within it.

The library uses the symbol font for some of the notation and formulae. If the symbols for the letters ‘alpha beta delta’ do not appear here [**a b d**] then the symbol font needs to be installed before all notation and formulae will be displayed correctly.

EGIRP | voltage source conductance current resistance power | [volts, V] [siemens, S] [amps, A] [ohms, W] [watts] | VXYZ | voltage drop reactance admittance impedance | [volts, V] [ohms, W] [siemens, S] [ohms, W] |