When two or more sources are present in a network and they are connected in such a way that they are not mutually in series or in parallel, special network solution methods like *mesh analysis *or *nodal analysis* must be employed. The application of these two techniques being described earlier for d.c. networks, they are well applied in a.c. network analysis too. The difference is that in a.c. application the *complex numbers* (i.e., impedances) are used as the *coefficient of the equations* (instead of real numbers i.e., resistances as done in d.c. applications) and the variable (like current and voltages) have phasors instead of scalar voltage or currents.

In addition to application of mesh or nodal analysis in a.c. networks, application of network theorems like *Thevenin’s theorem, Norton theorem *etc., are listed in this website. Since the discussion of theoretical aspects have been well covered in the dc, applications, hence in theoretical discussions regarding these theorems here, only the variations required in a.c. application are considered.

**Source Conversions**

When applying the network theorems in the a.c., networks, it may be necessary to convert a current source to voltage source and vice versa. This can be accomplished in the same manner as we do for d.c. networks, expect now we shall be using phasors and impedances instead of real numbers and resistors.

**Nodal Analysis**

*Node voltage analysis* of a.c. networks is identical to that of d.c. networks. In the frequency domain network having n-principle nodes, one of them is designated as the reference node and we require (n-1) node voltage equations to solve for the desired result. Regarding *sign convention* of nodal currents, we take the currents entering the nodes as -Ve while the currents leaving the nodes are +Ve.

**Independent and Dependent Sources**

The term *independent* indicates that the magnitude of the source is independent of the network to which it is applied and that is exhibits its terminal characteristics even if completely isolated.

A *dependent* or *controlled* source is that whose magnitude is governed by a current or voltage of the system in which it is situated.

The diagrammatic representation of the dependent sources is similar to that we have shown in analyzing the d.c. network.

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