# Current flow from higher to lower potential

Discussion in 'General Electronics Chat' started by aq_blues, Jul 20, 2011.

1. ### aq_blues Thread Starter New Member

Jul 20, 2011
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Hi All,
This morning I got my concepts shattered. I had started my engineering with this sentence: 'current flows from high potential to low potential'
This is evident in my first schematic where we see current flowing from +5V to -5V terminal.

But in my second schematic, I do not understand why the current would not flow from +5V to -5V termial. Instead, I see two currents. One flowing from +5V to ground and the other flowing from -5V to ground.

If anybody can shed some light, I would be thankful to him.
Thanks,

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2. ### Ron H AAC Fanatic!

Apr 14, 2005
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Current flows from + to -, as you said. See attachment.

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3. ### aq_blues Thread Starter New Member

Jul 20, 2011
12
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I understand the current flows. What I do not understand is, why the current would not flow from +15V terminal to -15V terminal. Why would it go to ground instead, where in the bottom it can see the -15V(which is lower potential than the gnd)(As said, Current flows from higher potential to lower potential and -15 is lower)

4. ### t_n_k AAC Fanatic!

Mar 6, 2009
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The center bridging link in the second schematic effectively de-couples the upper & lower parts of the original schematic. The two "halves" are then effectively two completely independent circuits insofar as the current flow in each case is concerned. The fact that they share a common link is irrelevant.

Interestingly you have nowhere designated on the schematics what you consider to be your ground point.

5. ### Jony130 AAC Fanatic!

Feb 17, 2009
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simply add resistor between +5V and -5V

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6. ### ErnieM AAC Fanatic!

Apr 24, 2011
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Here is another way of drawing your circuit:

Current requires a loop to flow. Voltage requires two points to establish a potential.

Neither exists between these supplies as they are connected at only 1 point.

7. ### GetDeviceInfo AAC Fanatic!

Jun 7, 2009
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the current does flow from +15 to -15, however, because the loads are not balanced, the difference in loop current flows through common.

8. ### ErnieM AAC Fanatic!

Apr 24, 2011
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Look again.
No current from the +15V battery goes thru the -15V battery.
No current from the -15V battery goes thru the +15V battery.

9. ### GetDeviceInfo AAC Fanatic!

Jun 7, 2009
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Current in the common leg is the sum of the two loops, and not actually flowing in both directions. Where does the difference flow?

10. ### ErnieM AAC Fanatic!

Apr 24, 2011
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Huh, well you got me there. The difference flows around the outer loop. Simple KCL applied to the two nodes of the middle wire.

What I find surprising is my drawing actually changed the circuit by adding two paths side to side. This allows each current to flow in it's own middle wire and thus there is a zero outer loop current.

Here the topology change actually changed the currents. This is a first for me.

11. ### strantor AAC Fanatic!

Oct 3, 2010
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as per your attachment, wouldn't that require current to flow in 2 different directions through the same conductor at the same time?

12. ### GetDeviceInfo AAC Fanatic!

Jun 7, 2009
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Actually hasn't changed the operation, just the perspective. Schematic drawing can assist or confuse. Speaking of such, let's hold on to that concept and jump to the other thread referring 'ground'.

13. ### t_n_k AAC Fanatic!

Mar 6, 2009
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It might be informative if one were to replace the "ideal" link with another ammeter (AM3). What would the ammeter indicate? In reality such a zero resistance link as proposed would not be physically realizable. In that sense there are not two nodes as the drawing implies - just one - as ErnieM's recasting of the drawing suggests...

I notice also that +15V and -15V crept in somewhere while the original schematics show the sources as V1 & V2 each of 5V.

As GetDeviceInfo's point infers, this has a lot to do with how one represents a conceptual circuit with a conceptual topology.

14. ### Ron H AAC Fanatic!

Apr 14, 2005
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I realize that most of you already know this, but here goes, anyhow:
Of course, the ideal ammeter will indicate the difference in the currents of the two loops. The ammeter will have zero volts across it.
The current in each battery and each resistor will be the same no matter which way the connecting node is drawn.

15. ### t_n_k AAC Fanatic!

Mar 6, 2009
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And hopefully that is the end of the discussion.

The OP's absence seems to indicate it ended for them some time back!