Network Analysis Flashcards
Methods of solving electrical networks
Superposition theorem
Kirchoffs Laws
Thevenin and Norton Equivalent Circuits
What is a passive networks
it contains no source of emf
What is an active network
it does contain an emf
What is superposition theorem
It is the process of considering each emf source in turn, with all other sources being represented by their internal resistance
resultant currents is obtained from algebraic sum of the currents from each source
In superposition theorem what should you do to voltage and current sources
short circuit voltage sources and open circuit current sources
If current is flowing into a battery what is happening
the battery is being charged
What is a node
the point where two or more branches meet
What is a branch
Part of a circuit connecting two nodes
What is a loop
closed path formed by connecting branches
What is kirchoffs first law
The algebraic sum of all the instantaneous currents entering any node is zero at all times
Kirchoffs second law
instantaneous voltages around a loop is zero at all times
When is thevenin theorem useful
when load resistance is changing saves having to reanalyse the whole circuit
How does Thevenin work
an active network having two terminals (A and B) can be replaced by a constant voltage source E, the magnitude of which is equal to the open circuit voltage between A and B and an internal resistance r, r is the resistance between A and B with the load disconnected and emf sources replaced by their internal resistance
Steps for Thevenin
short circuit voltage sources and open circuit current sources
ignore the load voltage for the mean time
calculate the total resistance = r
Calculate voltage across the terminals = E
What is a replacement thevenin circuit made up of
A voltage supply E with internal resistance r connected to two terminals, across which a load may be connected
What is a norton equivalent circuit
An active network having 2 terminal A and B can be replaced by a constant current source Is where Is is equal to the short circuit current at the terminals and a shunt resistance r which is equal to the resistance between A and B with the sources removed
Relationship between Norton and Thevenin resistance
they are both the same
Parts of a norton equivalent circuit
constant current source with a resistor of resistance r across it
Key step for norton
short circuit the terminals and find the current flowing through them
How to find the norton circuit from thevenin
the thevenin equivalent should be equal to the norton equivalent, so short circuit the thevenin circuit to find the current
When comparing circuits from one setup to the next generally what will it ask you to compare
the current coming from the source, across the entire circuits resistance
If a current source has infinite internal resistance what is the current across the load
as the internal resistance is infinite the load current will be equal to the current supplied by the current source
If multiple sources in thevenin and norton how should you proceed
Use superposition to find voltages across A and B
While working out thevenin emf what may the terminals be considered as
a voltmeter
