Basic Electrical Question

Factual Questions
1

This is a problem which has been bugging me for some time now.

Suppose you got two ideal voltage sources, one 15V the other 10V say, and grounded the two negative terminals. Then you connected both positive terminals to the same node. What would the voltage at the node be? Wouldn’t both voltage sources be trying to give the node a potential equal to there own?

Also wouldn’t the same problem arise for two ideal current sources in the same branch of a circuit?

Seeing as I am talking about ideal sources feel free to infrom me on how non-idealities would make this problem solvable. In other words does the fact that there is no such thing as an ideal voltage source make this problem impossible to solve?

2

It would short circuit. It’s the same thing is connecting a wire from the 15V to directly to ground. Only the difference becomes 5V instead of 15V

3

Dammit just realisesd that an earlier post of this question had posted even though the link timed out.

Cheers anyway.

4

Assuming the two sources have the same current output capacity, the lower voltage source would lose in this tug of war as it tried to draw current from the other source. This is why you are told to replace batteries (cells) in pairs instead of singly.

5

A voltage source can be pretty well modeled by an ideal voltage source with a series resistance. The beefier sources have a lower resistance. This means that as it outputs more current, the voltage at the output drops, because voltage is dropped across that resistor.

So if you draw a circuit with the voltage sources modeled as a V with a series R, it’s pretty easy to see what happens.