# Voltage sources in Parellel

Discussion in 'Electronic Design' started by [email protected], Dec 22, 2006.

1. ### Guest

Hello everybody,
What would happen if two voltage source are
connected in parallel.I think if the two voltages are of the same
voltage(say 'V') and amperage, the resultant voltage would be V itself.
But what happens if they are dissimilar(say 5 Volt and 3.3

Regards,
Robotnik

2. ### Andrew HolmeGuest

Real voltage sources have internal resistance. So there is always a (small)
resistor in series.

I think you are talking about ideal voltage sources, which do not exist. If
you connect dissimilar ideal sources in parallel, you get infinite current.
If you connect identical ideal sources in parallel, the voltage is indeed V
as you say; but if you connect a load, you cannot say how they share the
current drain. When you get infinity in the math, or too many unknowns, it
usually means the physical scenario is impossible in the real world.

3. ### LeftyGuest

Well an obvious example would be hooking two batteries of different
voltages in parallel, current would flow from the higher voltage to the
lower in the amount depending on internal resistenace of the battaries.

4. ### Jim YanikGuest

any Fluke differential voltmeter shows this.
They use a precision voltage source to buck against the measured
voltage,and use a null meter to zero out the current;then the Fluke readout
matches the unknown V source.

5. ### EmanueleGuest

ha scritto:
If You work in AC, take a double outputs transformer as example
in DC instead as same battery

So in general: in parallel --> sum the current
in series --> sum the voltage

If they are not similar all depend by the internal resistor
(be careful, can damage the voltage source)

Emanuele

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