Norton theorem was named after E.L Norton, formally
an engineer at Bell telephone Laboratory, USA. This theorem is an alternative
to the Thevenin’s theorem. In fact, it is the dual of Thevenin’s theorem.
Whereas Thevenin’s theorem reduces a two terminal active network of linear
resistances and generators to an equivalent constant voltage source and series
resistance, Norton’s theorem replaces the network by an equivalent constant-
current source and a parallel resistance.
an engineer at Bell telephone Laboratory, USA. This theorem is an alternative
to the Thevenin’s theorem. In fact, it is the dual of Thevenin’s theorem.
Whereas Thevenin’s theorem reduces a two terminal active network of linear
resistances and generators to an equivalent constant voltage source and series
resistance, Norton’s theorem replaces the network by an equivalent constant-
current source and a parallel resistance.
This theorem may be stated as follows:
i.
Any two terminal active network containing voltage source and resistances
when viewed from its output terminal is equivalent to a constant current source
and a parallel resistance. The constant current is equal to the current which
would flow in a short circuit placed across the terminals and parallel
resistance of the network when viewed from these open circuited terminals after
all voltage and current sources have been removed and replaced by their
internal resistances.
Any two terminal active network containing voltage source and resistances
when viewed from its output terminal is equivalent to a constant current source
and a parallel resistance. The constant current is equal to the current which
would flow in a short circuit placed across the terminals and parallel
resistance of the network when viewed from these open circuited terminals after
all voltage and current sources have been removed and replaced by their
internal resistances.
Explanation
Finding short circuit current (ISC)
The
Norton equivalent circuit contains an ideal constant current source of infinite
internal resistance and having a resistance of Ri connected in parallel with
it.
Norton equivalent circuit contains an ideal constant current source of infinite
internal resistance and having a resistance of Ri connected in parallel with
it.
i.
Another useful
generalization of this theorem is as follows:
Another useful
generalization of this theorem is as follows:
The
voltage between any two points in a network is equal to ISC x Ri
where ISC is the short circuit current between the two points and Ri
is the resistance of the network as viewed from these points with all voltage
sources being replaced by their internal resistance (if any ) and current
sources replaced by open circuits.
voltage between any two points in a network is equal to ISC x Ri
where ISC is the short circuit current between the two points and Ri
is the resistance of the network as viewed from these points with all voltage
sources being replaced by their internal resistance (if any ) and current
sources replaced by open circuits.
Suppose,
it is required to find the voltage across R3 and current through it
in figure 4 shown below
it is required to find the voltage across R3 and current through it
in figure 4 shown below
