# A Question about Voltage Sources in Parallel

• bibo_dvd
In summary, The circuit is very unrealistic since voltage sources are not normally put in parallel for two reasons: (1) If they are ideal voltages sources with the same voltage then one of them is redundant and if they are NOT the same voltage then they create a contradiction by definition; (2) If they are not ideal voltage sources then one of them will have a slightly higher voltage and may damage the other one.

#### bibo_dvd

Hello Guys !

My Question : in this photo i found That Total Resistance will be = 7 ohm .

and I2 = 12 / 7= 1.71 A and I1 = 0.5 * I2= 0.5 * 1.71= 0.85 A

I can't understand why I1= 0.5 I2 ?? and why it isn't the same of I2 ??

here is the photo

Thank you Guys !

The circuit is very unrealistic since voltage sources are not normally put in parallel for two reasons:

(1) If they are ideal voltages sources with the same voltage then one of them is redundant and if they are NOT the same voltage then they create a contradiction by definition
(2) If they are not ideal voltage sources then one of them will have a slightly higher voltage and may damage the other one

That said, the circuit as drawn, assuming ideal voltage sources, should have I1=I2

phinds said:
The circuit is very unrealistic since voltage sources are not normally put in parallel for two reasons:

(1) If they are ideal voltages sources with the same voltage then one of them is redundant and if they are NOT the same voltage then they create a contradiction by definition
(2) If they are not ideal voltage sources then one of them will have a slightly higher voltage and may damage the other one

That said, the circuit as drawn, assuming ideal voltage sources, should have I1=I2

This is not correct.

I1 is the current from 1 battery, I2 is the current from both batteries so will be double I1.

Note that this is a very common configuration is small battery driven devices.

No. I2 is the combined current of I1 and the current which is not labeled from the rightmost 12 volt battery. The drawing is crowded together so it makes it looks like I2 is the current in the rightmost battery.
-
Now as far as voltage sources not normally put in parallel. That is a stretch. Many 12 volt automotive batteries are in parallel in diesels due to the higher starter current required. Semi tractors can have more than 2 in parallel. Don't get me wrong, there can be issues associated with voltage sources in parallel but it doesn't apply in this thread since the problem said to assume ideal supplies.

Edit: Integral beat me to it.

Integral said:
This is not correct.

I1 is the current from 1 battery, I2 is the current from both batteries so will be double I1.
QUOTE]

OOPS

I1 is definitely half of I2, if both are matched voltage source. There is no doubt about it.

What I am thinking is that this schematic can't be analyzed using superposition theorem. So it might not be realistic. For starter circuits, do all voltage sources (in parallel) operate in normal mode or are switched out ?

## 1. What is the purpose of connecting voltage sources in parallel?

Connecting voltage sources in parallel allows for an increase in the total amount of current that can be delivered to a circuit. It also ensures a constant voltage across all connected components.

## 2. Can different voltage sources be connected in parallel?

Yes, different voltage sources can be connected in parallel. However, it is important to make sure that the voltage ratings of each source are compatible and will not cause any damage to the circuit.

## 3. How do voltage sources in parallel affect the overall resistance of a circuit?

When voltage sources are connected in parallel, the overall resistance of the circuit decreases. This is due to the fact that the current is split between the sources, resulting in a decrease in the total resistance.

## 4. What happens to the voltage when multiple sources are connected in parallel?

When multiple voltage sources are connected in parallel, the voltage remains constant across all connected components. This is because the voltage sources are all connected to the same points in the circuit.

## 5. Is it possible for voltage sources to be connected in parallel without causing any issues?

Yes, it is possible for voltage sources to be connected in parallel without causing any issues. However, it is important to ensure that the voltage sources are compatible and that the total current drawn from the sources does not exceed their capabilities.