无约定条件下能否谈及绝对电压？技术问询

Great question—this gets straight to a core nuance of how we frame electrical potentials in physics and engineering. Let’s break this down in practical terms:

• Everyday voltage is always a difference: In nearly all real-world scenarios (circuit design, power grids, basic electronics), we only care about potential differences. Even when dealing with time-varying magnetic flux (which induces EMF), we’re still measuring a loop-wide potential difference that drives current. These cases don’t need an absolute reference because all measurable effects (current flow, power dissipation, charge movement) depend entirely on the gap between two points.

• "Absolute voltage" is a convention, not a fundamental truth: When we talk about an absolute voltage (like defining a point’s potential relative to infinity), we’re leaning on an explicit, arbitrary agreement. The choice to set infinity’s potential to 0 is just that—a convention. There’s no physical law mandating this; we could just as well pick Earth’s surface (the "ground" reference in most circuits) or any other point as our zero baseline. The "absolute" value only has meaning because we all agree to use that reference.

• Why this convention works: Adding a constant value to every potential in a system doesn’t change the electric field (the gradient of potential) or any observable behavior. All the stuff we actually measure—force on a charge, energy transferred, current speed—depends on differences, not absolute numbers. So the convention is useful for calculation, but it’s not inherent to the physics.

• A quick sanity check: Without a convention, "absolute voltage" would be completely meaningless. You could shift the entire potential scale by 50V or 500V, and nothing in the physical system would change. That’s a clear sign absolute voltage can’t exist without an agreed-upon reference point.

In short: There’s no such thing as an absolute voltage definition that doesn’t rely on a convention. The "absolute" values we reference are just potentials measured against a universally accepted (but arbitrary) baseline like infinity or ground.

内容的提问来源于stack exchange，提问作者Carvo Loco