How realistic is the term "ground"

  • Context: Undergrad 
  • Thread starter Thread starter Samson4
  • Start date Start date
  • Tags Tags
    Ground Term
Click For Summary

Discussion Overview

The discussion revolves around the concept of "ground" in electrical systems, particularly in relation to large bodies like the Earth and oceans. Participants explore the implications of using these bodies as reference points for voltage, the behavior of electrical systems involving such references, and the theoretical scenarios involving devices like Van De Graaff generators.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants question whether the Earth or large bodies like the ocean can be considered useful sources of charge, particularly in the context of a Van De Graaff generator.
  • Others argue that the concept of ground is primarily a reference voltage defined as zero, which may not necessarily correspond to the physical ground.
  • A few participants highlight that while the Earth and oceans are good conductors, they may not effectively function as capacitors due to their conductive properties.
  • Some contributions suggest that the capacitance of the Earth is limited and question the implications of this for measuring potential differences in practical scenarios.
  • There is a discussion about the arbitrary nature of defining ground and how it relates to voltage measurements in circuits.
  • Participants express uncertainty about the practical applications of using large bodies as capacitors and the implications of surface charge influences.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the utility of large bodies as sources of charge or the implications of using them as ground references. Multiple competing views remain regarding the definition and practical application of "ground" in electrical systems.

Contextual Notes

Limitations include the dependence on definitions of ground, the assumptions about the behavior of large conductive bodies, and unresolved questions about the practical implications of using these bodies in electrical systems.

  • #31
The Earth is a conductor. All conductors have capacitance as well as resistance and inductance as small or large as those values may be. It is possible to claim a capacitance for the Earth but it also has to be between two specified points. Trying to assign a value to the Earth in general may be meaningless since if it were possible to stick a probe at either end of the Earth and measure, values would vary depending on the location of those two points.

The term ground comes from a time in early physics when Earth ground and electrical ground where the same thing. The term is still used as the zero reference for electric potential, but ground for a circuit and ground for the Earth may or may not be at the same potential. In circuit analysis you can assign zero potential to any node calling it ground and calculations are still valid.

For example utility electrical systems use a ground that is in fact Earth ground. However a device not in contact with Earth ground may have a ground with higher or lower potential. The problem is sometimes ground is in fact Earth ground and sometimes it's only a common node in a circuit used as a zero reference. It's a term that does a poor job of clarifying itself.
 
Last edited:
Physics news on Phys.org
  • #32
kuruman said:
The "Volts" are an electric potential. You can raise your body's electric potential to many Volts (don't try it) and not be harmed as long as you make sure that your entire body is an equipotential and you are far from objects across which a spark can jump at you. Again, don't try this. What is harmful, is a potential difference or voltage between two points in your body because then a current (amps) flows between these two points according to Ohm's law and, if your heart happens to be in the way, its electrical signals get messed up and goes into atrial fibrillation which could be lethal. It's a hard way to learn the difference between electric potential and voltage. :smile:
I'm rather partial to the auld heart all the same, so I think I'll pass on sending any unnecessary volts through this crumbling body of mine.
 

Similar threads

High School How Is Electric Potential Difference Measured Without Specific Distances?
  • · Replies 8 ·
Replies
8
Views
2K
Undergrad Let current from a Van de Graff generator flow through you
  • · Replies 5 ·
Replies
5
Views
4K
Undergrad Possible to Store Energy in Ionized Gas?
  • · Replies 2 ·
Replies
2
Views
2K
Undergrad Lichtenberg Figures: Positive & Negative Discharges on Plastics & Acrylic
  • · Replies 2 ·
Replies
2
Views
3K
Undergrad Confused about electrostatic voltage and DC voltage
  • · Replies 1 ·
Replies
1
Views
2K
Undergrad Power line workers and voltage
  • · Replies 5 ·
Replies
5
Views
5K
Is my fictional Solar System stable and realistic?
  • · Replies 21 ·
Replies
21
Views
6K
Undergrad How does Lord Kelvin's water drop electrostatic generator work?
  • · Replies 1 ·
Replies
1
Views
8K
Graduate Magnetostatics: What if "steady" currents were divergent?
  • · Replies 6 ·
Replies
6
Views
2K
Question about the Earth acting as a conductor/ground
  • · Replies 1 ·
Replies
1
Views
2K