Network Theorems in Current Electricity

For electrical conduction through a conducting medium, the current flow is made through out the medium under certain potential drop applied across it. Basically here in this case, when external applied field, the quasi free electrons inside that conducting medium will experience an accelerating force in a certain direction and as a result, they will become accelerated and possess a certain drift velocity when estimated theoretically over the duration of relaxation time. This drift motion of conduction electron is the basis of electrical conduction within a conductor. This gives current flow and hence current density inside that medium for the flow of charge in unit time through unit cross section inside the conducting medium.

The current flow is then will be restricted by the resistance of the medium by obeying Ohm's law and in that case the electrical conductivity of the medium will be successfully defined. This electrical conductivity and hence the reciprocal of it i.e. the resistivity of the medium will be taken as the characteristics features of that medium and they will extremely depend on the carrier concentration gradient of the medium. This current flow inside the conductor at the time of electrical conduction will also become guided by equation of continuity which is based on the conservation of charge and that will be restricted by certain boundary conditions of electrodynamics.

The flow of current in any complicated bilateral electrical network can primarily be analyzed by Kirchhoff's current law and voltage law, and these laws on the basis of charge and energy conservation can also be applied to several basic network theorem like Maximum Power Transfer Theorem, Reciprocity Theorem of electrodynamics, Superposition theorem etc. and they can also be applied to unbalanced Wheatstone bridge. Again the sensitivity of such unbalanced Wheatstone bridge can be enhanced by Calendar's method.

In this context regarding network analysis in electrodynamics, another two significant theorems are Thevenin's theorem and Norton's theorem where in each theorem, any complicated network can simply be replaced by equivalent simple circuit with the successful use of equivalent voltage source and current source respectively across the output load of the original network. Last of all, the other way for network analysis in basic level, the star - delta conversion is needed and the idea is taken from the features of equivalent T section network and pi section network respectively.