P
2A
= V. I = 10 × 2 = 20 watt (P
delivered
)
P
10Ω
= I
2
. R = 1
2
× 10 = 10 watt (P
absorbed
)
Pdelivered = Pabsorbed = 20 watt
Hence Tellegen’s theorem is verified.
Substitution Theorem Statement:
The voltage across and the current through a Branch
in a bilateral network is
known, the branch can be replaced by any combination of elements in such a way that the same
voltage will appear across and same current will pass through the chosen terminals. In other
words for branch equivalence the terminal voltage and the current must be same
.
This is illustrated with a simple circuit shown in the figure below.
Figure: (a) A simple DC circuit to explain the substitution theorem.
In this circuit the load resistance
R
L
is the branch being considered for equivalence. The current
I
through the load resistance
R
L
= 24/(3+5) = 3 A.
Figure: (b) Equivalent branches across terminals ‘xy’
In figure (b) above several equivalents of branch
‘xy’
are shown. It may be noted
that in all the cases the terminal voltage across and the current through the equivalent branch are
the same as
that of the original branch
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