Thevenin's Theorem

Any two networks having e.m.f and impedance can be replaced by an equivalent network with e.m.f and impedance

Importance of Norton's and Thevenin's theorem

Interchange of voltage and current sources by means of Thevenin's and Norton's theorem provides a powerful method of circuit analysis. In such conversion, it should be noted that a voltage source is removed from a circuit by short circuiting its e.m.f whereas a current source is removed by opening its circuit. An example of this is given below

From fig a, the portion of the circuit to the left of the terminals a, b may be transformed by Norton's theorem to fig b, Z1 and Z2 combined in parallel as admittances and circuit to the left of c, d changed back by Thevenin's theorem to figure b. Z1 and Z2 combined in parallel as admittances and the circuit to left of c, d changed back by Thevenin's theorem to that of fig c. One more transformation by Norton's theorem would give a current sources circuit from which the load voltage can be readily calculated. Fig c which are obtained through use of Thevenin's theorem, The load voltage is given by

It may be noted that these two evaluations are of the identical mathematical form, but one relates voltages and impedances and another currents and admittances. Thus the voltage source and current source circuits are duals.

Lattice Network

A network in which we solve more and more complicated networks by using various Networks by using various Networks laws such as Thevenin's theorem, Norton's theorem, Reciprocity theorem etc is referred as lattice network.

Expression for sensitivity in ac bridge

When a=1

Z1/Z3= Z2/Z4 =1

Z1= Z3

Z2= Z4

Hence, the sensitivity of bridge be maximim when a=1

i.e Z1=Z3, Z2= Z4

Power supply must be increased when the value of Z1 is exceedingly high. At the mean time value of Z3 also has be be increased to avoid the damage of Z1 with infinite (Z1/Z3) and E, the sensitivity of bridge is observed to be three time large taking a= 0.2 as compared to that a=1.

This note is taken from Classical Mechanics, MSC physics, Nepal.

This note is a part of the Physics Repository.

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