# Is absolute electric potential arbitrary?

Does it all depend on the reference point, for example is there a true ground potential? Is the true ground potential one referenced with infinity? Thanks

• There is no such thing as absolute potential, it is all relative. – PlasmaHH Feb 13 '18 at 9:50
• What voltage exists between the earth and the moon? – Andy aka Feb 13 '18 at 10:05
• Depends on solar activity. – Janka Feb 13 '18 at 10:17
• @PlasmaHH Yes, there is such a thing as absolute potential...ask a physicist. However, it doesn't have much practical value for engineers. – Elliot Alderson Sep 23 '19 at 11:57

As discussed in your previous question there isn't any point worrying about this. You can't run a wire to infinity to measure the potential with respect to that.

Pretty much everything you will be working on will require that you connect the black lead of your meter or the ground clip of the scope to some reference point that is within reach. The closest thing to true ground potential you will get is the planet Earth but even this has variations due to the sometimes surprisingly poor conductivity of the earth in some locations.

I disagree with the answers above, electric potential like speed is absolute and limited, in fact the two ratio's are related. Speed is defined as x/t or distance over time and electric potential is E/q or energy over charge.

All it takes is a simple thought experiment to prove that electric potential is limited.

Take two electrodes define one as the anode and one as the cathode, now imagine moving all the electrons to the cathode and all the protons to the anode, and even a child can understand that a limit has been reached.

Consequently it can be understood that such absolute potential which exists between the two electrodes is indeed equivalent to the potential that exists between a single electron and a single proton i.e. the H atom.

It is indeed 938 million volts, which is also absolute maximum potential, so by definition any value that has an absolute maximum must also have an absolute minimum, in this case zero electric potential.

...and yes there is such a thing as true ground potential and you can indeed work it out by knowing the mass of the electron.

• I think the question was not about whether there is a maximum limit to voltage but whether there is an absolute zero. I believe the use of the word "infinity" by the OP may have been a language issue. Having said that, this is an engineering site and not a physics site, so your "thought experiment" is not of much value to us here. – Elliot Alderson Sep 23 '19 at 11:56
• Welcome to EE.SE, Stephen. "I disagree with the answers above ..." Note that answers float up and down with votes and user sorting preferences. – Transistor Sep 23 '19 at 16:33

The electrical potential is defined only in terms of differences. That means the potential difference between two points can be calculated, but there is no absolute definition of the electrical potential at one singular point.

The Earth is generally considered to be the zero potential value because everyone is on it and therefore has a similar charge in various points of it. Any different charge from that average would be observable as a potential. So the fact that Earth is considered zero potential is just a convention.

A true zero potential would be an area somehow isolated from everything, including from the general cosmic field and that contains nothing inside (like no particles, no fields of any kind).

True zero potential would be like the equivalent of absolute zero in temperature. We know one exists but we can't actually obtain it.