two supply in parallel and two current sources in series- what will happen?

[SherlockBenedict]

What will happen if I connect two voltage sources say 5V and 3V in parallel? Assume that they are not ideal and possess internal resistance. What will be the equivalent voltage?

Similarly what will happen if we have two practical current sources (say 1A and 5A) in series?


Thanks a lot.

 

[FvM]

Two options:
- the sources are ideal besides finite internal resistance. You can transform voltage to current sources and vice versa and also calculate a resulting source according to linear network laws.
- the sources are real also in other regards, involving non-linear properties like current or voltage limits. Then linear network theory can't predict the result, you need a non-linear solver or similar methods to determine the behaviour of the combined circuit.

 

[rfredel]

Hello,

if you connect two voltage sources with different Voltages in parallel mode, a compensating current will flow between the sources. For example two different batteries will connec together, the battery with the higher voltage try to charge the other, until both batteries have the same voltage.

In the other case you put differnt sources in series. The voltages of both sources will add together, but you can only take the lowest current.


Regards

Rainer

 

[FvM]

if you connect two voltage sources with different Voltages in parallel mode, a compensating current will flow between the sources. For example two different batteries will connec together, the battery with the higher voltage try to charge the other, until both batteries have the same voltage.

In the other case you put differnt sources in series. The voltages of both sources will add together, but you can only take the lowest current.

Similar to the first case, where the resulting output voltage can be higher than the smaller of the two individual sources, the resulting output current of two series connected current sources with internal resistance can be higher than the "lowest" current. Otherwise you're assuming specific constraints that are not mentioned in the question.

 

[jasonc2]

Adding detail to FvM's reply (the first case): If your voltage and current sources are non-ideal except for internal resistances you can convert single sources or the entire network as a whole into a single voltage source with a series resistor or a single current source with a parallel resistor using thevenin's or norton's theorems, respectively, which is a straightforward way for you to calculate the effect of arbitrary voltage/current/resistor networks.

There is a neat animated online circuit simulator here that is useful for helping to answer these types of questions: https://www.falstad.com/circuit/ (It's in Java, if it asks you to run it say yes) if you approximate non-ideal non-reactive current and voltage sources with ideal components (series resistor for internal resistance of voltage source, parallel resistor for internal resistance of current source).

Here I have set up a simulation illustrating your question (with arbitrary internal resistances that I picked). I have also set up thevenin and norton equivalents of each: https://tinyurl.com/bsc2mpd (maximize window to see whole thing).