# Voltage Drop and Cord Length?

Discussion in 'Power Electronics' started by tomadom, Apr 26, 2019.

38
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Jan 18, 2013
If I have a power source and a single lead coming out of this power source, and that lead branches out to multiple different connection types, do those extra fingers attached to the end of my power cord contribute to voltage drop?

For example. See picture below.

Last edited by a moderator: Apr 26, 2019
2. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,491
2,833
Jan 21, 2010
Yes, but only for the portion of the load connected to them.

For illustrative purposes you could assume that each load is a constant current, and that each length of wire has a small fixed resistance. If you assume this is connected to a constant voltage source, you can then perform some simple math to show where voltage drops occur. To know what the actual voltage drops are you need to know the actual resistance of the wires and the characteristics of both the voltage source and the loads.

3. ### Bluejets

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Oct 5, 2014
Or stick a volt meter on the end of each under load.
If less than 5% of supply authority level, you're sweet.

38
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Jan 18, 2013
So to be clear, what I'm asking is if I only connect one device to one of these fingers, will the other fingers (not connected to anything) cause some voltage drop?

5. ### Bluejets

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Oct 5, 2014
Nothing connected to say branch 2,3,and 4 so no.
Only the one with a load, that's how voltage drop works.
The more load, the more voltage drop.

6. ### Nanren888

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Nov 8, 2015
>>So to be clear, what I'm asking is if I only connect one device to one of these fingers, will the other fingers (not connected to anything) cause some voltage drop?

Cause voltage drop? No. Not if they don;t draw any current.
Experience voltage drop? Yes. Because the first cord is shared & has current flowing through it, hence the others tap off a point that already has a voltage drop. But if there is nothing connected to the others, then it does not matter much. Seems a pretty academic question?

38
0
Jan 18, 2013
The length of the cord can contribute to voltage drop. This is indeed true.
So it seems, from the answer above, that it's a matter of displacement and not shared volume of the conductor that's important.

I've been trying to narrow down a problem with voltage drop in the scenario I have described. Hence the question!

8. ### dave9

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Mar 5, 2017
It would probably be more effective to have just detailed what these circuit(s) are, and whether your power source is regulated in which case you should be able to roughly calculate the voltage drop as the series of resistances the wires impose.

Generally if power delivery, use a lower gauge wire on each leg proportional to the current that leg carries.

Last edited: Apr 26, 2019
9. ### Bluejets

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Oct 5, 2014
I'd suggest you do as dave9 says.
As it is, one is tending to stand on one's head to decipher just where you are going and what you are describing.
In other words, over-complicating the matter.

10. ### Nanren888

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Nov 8, 2015
So this is mains power, right? Is the power source end a wall socket?