A little confusion on my part. I see that a volt is the SI unit of electromotive force as the Wikipedia may show.

I also see that One Volt is defined as energy consumption of one joule per electric charge of one coulomb. Or. 1 ampere of current against a one ohm resistance.

One joule is equal to the work it takes to make a watt of power for a second, or to move a body one meter with a one-Newton force.

In the first definition there is no time dimension but then in the second definition a time dimension mysteriously shows up. Does the definition depend on the context perhaps?

  • \$\begingroup\$ Does (potential energy/charge) equal to energy? \$\endgroup\$
    – Long Pham
    Commented Dec 9, 2018 at 16:48
  • 2
    \$\begingroup\$ Would you be in such a quandary if I said that the velocity of a moving object is \$\frac{dw}{dp}\$ i.e. it is the rate of change of energy with respect to momentum? If I then redined it as distance/time would you be concerned? \$\endgroup\$
    – Andy aka
    Commented Dec 9, 2018 at 17:34
  • \$\begingroup\$ @Long ...are you saying a volt is a measure of potential energy ? \$\endgroup\$
    – Sedumjoy
    Commented Dec 9, 2018 at 18:52
  • \$\begingroup\$ @Andy aka.....no I am OK with that ...so please look at my comment below to TimWescott and tell me if you agree ? if volt was expressed as a time rate change it would solve my problem ....i have not seen that yet \$\endgroup\$
    – Sedumjoy
    Commented Dec 9, 2018 at 18:53
  • \$\begingroup\$ But how can you be happy with that; momentum and charge are identical in the respective solutions for velocity and volts and what has velocity got to do with time that makes it easy to understand whereas with voltage, the time thing stumps you. The derivations are identical for voltage and velocity so now you confuse me. \$\endgroup\$
    – Andy aka
    Commented Dec 9, 2018 at 21:12

1 Answer 1


The volt is neither a measure of force or of energy consumption. That's why it is its own unit.

The term electromotive force is a metaphor for voltage as a force, because it explains current going through a resistance by analogy to water under pressure going through a pipe. But a volt is not a force.

A volt is a measure of electric potential, and electric potential is it's own thing. Any analogy to any familiar process will have flaws, so if you hold too tightly to them you'll be confused. But (to go and use a different metaphor) a volt is a measure of how "far" some charge has been "lifted" in an electric field. It is analogous to, but not the same as lifting a rock in a gravity field. If you lift a 1 kg rock 1 meter at the surface of the earth (where \$g=9.8 \frac{\mathrm{m}}{\mathrm{s^2}}\$ acceleration), you will have increased it's energy by \$9.8 \mathrm{J}\$. But the acceleration due to gravity isn't a force, or an energy -- it's an acceleration due to gravity, and if you take mass to be analogous to charge, then it is height that is analogous to voltage.

So gravity is a fundamental force, and the gravitational potential within a gravity field is "height". Electrostatic attraction (or repulsion) is a fundamental force, and the electric potential within an electric field is voltage, or EMF.

  • \$\begingroup\$ I'm with you @TimWescott and I see the analogy however gravity is a fundamental force and a volt is not BUT is it the case that volt represents the fundamental force of electromagnetism and it is called "electromotive" force? and there lies the rub \$\endgroup\$
    – Sedumjoy
    Commented Dec 9, 2018 at 18:51
  • \$\begingroup\$ Answer edited. See the (new) last paragraph. \$\endgroup\$
    – TimWescott
    Commented Dec 9, 2018 at 20:20

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.