Draw the characteristics of ideal voltage and ideal current sources.
Answers
Answer:
The ideal voltage source has a constant voltage across its terminal, irrespective of the current drawn from the source. The ideal voltage source can supply any amount of current to the load. So, the ideal voltage source can supply unlimited power.
We are dealing with ideal situations and so the answers given must be respected as being those of ideal situations and must not in any manner change the characteristic of the ideal sources.
a. First take two different ideal current sources in series. If say, each ideal current source has 3 amps flowing, then when they are in series, connected in the same direction then one will sink its full 3 amps into the other and the connection point will have no accumulated extra current. Considering the two free ends, at one end the 3 amps will flow out while at the other free end 3 amps will flow in through infinity path and so infinity voltage will form across the two free ends to force the 3 amps to flow through an open circuit.
If the two ideal current sources are connected in opposite direction, then the connection node will accumulate 6 amps and hence have to force out 3 +3 amps into two open circuits and each of the two free ends will sink in 3 amps whereas across each current source there will be infinity voltage. ( two open circuits)
If the ideal current sources had 3 amps and 5 amps, then when connected in series in the same direction the connection point will sink out 2 amps into infinity which will return to the 5 amp source with the 3 amps from the other current source. Across each ideal current source, infinity voltage will appear.
If they are connected in series in the opposite direction then the connection point accumulate 8 amps and so it will have to throw out 8 amps where 3 amps will return to its relevant in side of one source while 5 amps will return to its relevant in side of the other source where both ideal current sources will have infinity voltage across them .
With two voltage sources connected in parallel, if they have equal voltage across there output, there is a voltage but no current, while if they are of different voltage there will be an infinite current flowing through them where there will be so much imaginable current flowing that this will produce their difference of voltage across the passive zero impedance connection.
Note that this is purely an ideal situation where, in an ideal current generator with its active infinite internal output impedance, an infinite voltage can pass the current output decided by the ideal current generator through a passive open circuit acting as load , while in an ideal voltage source, with its active zero internal impedance, it can pass infinity current through a passive zero impedance acting as load, to produce the voltage of an ideal voltage source across it. Practically it all sounds like a fairy story, but this is an ideal situation and it will have to be like that as otherwise both the ideal voltage source and the ideal current source will lose their defined characteristics.
It is interesting that in this ideology, there is room to define the following:-
A passive zero impedance acting as a load , may have a voltage across it only when connected to an ideal voltage source.
A passive infinite open circuit acting as a load, may have a current through it only when connected to an ideal current source.
An active zero internal output impedance as found in an ideal voltage source can have a voltage across it.
An active infinite, open circuit internal output impedance as found in an ideal current source can have current through it.
One does feel that comprehending such situations would make an easier understanding of circuits as the output of the transistor BJT when taken from the collector and when the output of the BJT is taken from the emitter. Also it could shed some light why it is never advisable to put a voltage source at the base of a BJT and a large capacitor at the emitter at the same time, where it is the imperfections of the situations that come to the aid of many engineering students!
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