A Question about Voltage Sources in Parallel

Click For Summary

Discussion Overview

The discussion revolves around the behavior of voltage sources connected in parallel, specifically addressing the relationship between the currents I1 and I2 in a given circuit configuration. Participants explore the implications of using ideal versus non-ideal voltage sources and the realism of the circuit presented.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions why I1 is equal to half of I2, seeking clarification on the current distribution in the circuit.
  • Another participant argues that if the voltage sources are ideal and have the same voltage, I1 should equal I2, suggesting that the circuit is unrealistic.
  • A different viewpoint asserts that I1 is the current from one battery while I2 represents the combined current from both batteries, indicating that I2 would be double I1.
  • One participant points out that the drawing may misrepresent the current flow, clarifying that I2 is not solely from the rightmost battery.
  • There is a mention of practical applications where voltage sources are used in parallel, such as in automotive batteries, countering the claim that this configuration is unrealistic.
  • Another participant emphasizes that if both voltage sources are matched, I1 will indeed be half of I2, but questions the applicability of the superposition theorem in this scenario.

Areas of Agreement / Disagreement

Participants express differing views on the behavior of currents I1 and I2 in the circuit, with no consensus reached on the correctness of the initial assumptions regarding the parallel voltage sources.

Contextual Notes

Participants note that the assumptions regarding ideal voltage sources and the implications of using superposition may limit the analysis of the circuit.

bibo_dvd
Messages
37
Reaction score
0
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

EbAEdiB.png



Thank you Guys ! :))
 
Physics news on Phys.org
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:redface:
 
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 ?
 

Similar threads

Engineering Calculate the power of the coils in this RLC circuit
  • · Replies 12 ·
Replies
12
Views
2K
Engineering Computing the Maximum Power delivered to a Resistor
  • · Replies 7 ·
Replies
7
Views
2K
Engineering AC Circuit Phasors: Find I1, I2, I3
  • · Replies 26 ·
Replies
26
Views
3K
Engineering Open-circuit voltage in Thévenin equivalent
  • · Replies 4 ·
Replies
4
Views
3K
Engineering Combination circuit with Series & Parallel light bulbs
  • · Replies 4 ·
Replies
4
Views
2K
Engineering How Do You Solve a Parallel Circuit Problem with Unequal Currents?
  • · Replies 8 ·
Replies
8
Views
3K
Superpostioning of an inpendent voltage and current source with depend
  • · Replies 3 ·
Replies
3
Views
2K
Should same values of currents be used in Kirchoff's laws?
  • · Replies 5 ·
Replies
5
Views
2K
Engineering Calculating Norton Equivalent Circuit for Complex Load Impedance
  • · Replies 2 ·
Replies
2
Views
2K
Leq = (L1*L2-M^2)/(L1*L2-M^2)Hope this helps
  • · Replies 108 ·
4
Replies
108
Views
36K