# Voltage on negative side

Discussion in 'General Electronics Chat' started by Webby, Jul 24, 2014.

1. ### Webby Thread Starter Active Member

Jun 15, 2008
66
0
What does a loss of voltage on the negative side of a circuit mean with a 12v circuit? How can there be voltage on the negative side of the circuit?

2. ### ericgibbs AAC Fanatic!

Jan 29, 2010
2,502
380
hi webby,
Sorry I do not not understand your question.

Could you please rephrase it or give an example.?

E

3. ### shell.albert New Member

Jul 23, 2014
8
0
confused question.

4. ### inwo Well-Known Member

Nov 7, 2013
2,433
315
Do you mean voltage drop in the negative lead of battery, or power supply?

Same as positive side! The "negative" just refers to the polarity or direction of flow.

Just as flow to a hydraulic motor can have pressure drop in either or both supply lines.

5. ### wayneh Expert

Sep 9, 2010
12,100
3,034
Like water, electricity flows from uphill (V+) to downhill (V-). (This is an arbitrary convention, the electrons actually move in the opposite direction.)

Like a pond on a mountain, no electricity will flow unless there is a path to a lower voltage. So we label the higher voltage as positive, and the lower voltage as negative or zero. All that matters is the voltage difference between them, same as elevation change for water.

On a power supply and in many schematics, a voltage labelled as negative may well be below some other reference point such as common or ground. Like a valley compared to the plains above.

6. ### Webby Thread Starter Active Member

Jun 15, 2008
66
0
What I mean is if the voltage is lost on the negative side of a 12v circuit how will this effect the consumer?

7. ### MrChips Moderator

Oct 2, 2009
12,432
3,360
What do you mean by "voltage is lost"?

What do you mean by "negative side of a 12v circuit"?

What do you mean by "consumer"?

You make no sense whatsoever to me.

8. ### inwo Well-Known Member

Nov 7, 2013
2,433
315
Same as voltage lost on the positive side.

If enough voltage is lost or circuit is open the consumer will get less or no current.

Draw a picture.

9. ### Webby Thread Starter Active Member

Jun 15, 2008
66
0
Thanks inwo... On a 12volt circuit what determines the voltage drop to earth I.e when measuring with a meter what is the maximum you should see on a earth side of a circuit

10. ### ian field Distinguished Member

Oct 27, 2012
4,413
782
If you lose too much voltage on the supply cables - use thicker cables.

11. ### MrChips Moderator

Oct 2, 2009
12,432
3,360
Still makes no sense. Why don't you draw a picture?

Scenario #1. You measure voltage with a voltmeter: RED lead connected to -VE battery terminal, BLACK lead connected to EARTH GROUND. Reading should be 0V. There is no connection to EARTH GROUND.

Scenario #2. The -VE terminal of the battery is connected to EARTH GROUND.
Reading on the voltmeter should be 0V. There is no difference in potential between the -VE terminal and EARTH GROUND.

12. ### inwo Well-Known Member

Nov 7, 2013
2,433
315
If by earth you mean a large metal structure used as a common for the negative connections, then the voltage from battery - to ground is determined by current draw and (- to ground) wire size.

Generally from near zero to a fraction of a volt.

13. ### MrChips Moderator

Oct 2, 2009
12,432
3,360
Gleaning from your other posts, maybe this is what you are referring to:

Senario #3: You are working on a 12V automotive system.
You connect the BLACK lead of a voltmeter to CHASSIS.
You connect the RED lead to the RETURN side of a circuit.

You should see no greater than 0.1V (I'm guessing, without actually testing this.)

As others have said, you need thicker cables.