What is electromotive force? What's its relationship to Voltage?

[StoicIndieHacker369]

TL;DR Summary

This was a question that I posted on the Physics stack exchange, but I'm posting it here to have a higher probability of receiving an adequate answer.

This is the question:

What is electromotive force? What's its relationship to Voltage? + clarification of confusion

If you believe you have a good answer, please answer either in this website or in Stack Exchange.

 

[Dale]

It is fine to post the question on both sites, but not this way. The question should be self contained on each site so that people can understand what you are asking on each site directly.

 

[PhysicsEnjoyer31415]

I will answer your question but only the one here on PF.

Electromotive force is basically the potential difference between two points before they are connected .

Now there are two cases after connection is made between the points of 2 different potentials

Case 1: EMF = Voltage
This happens when there is no resistance and no loss of energy (only possible in ideal circuits) and there is no internal resistance in the voltage source

Case 2: EMF > Voltage
This happens in practical circuits we see in daily life . Here the components have resistances , charges leak , voltage source has internal resistance and energy is lost as heat/light .

Voltage can never be greater than EMF as EMF is a perfect tendency or a perfect potential difference(EMF is in a open circuit ) but voltage is the the result of applying EMF in a closed circuit

 

[phinds]

In circuit analysis, voltage at a the output terminals of a power source that is open circuit is taken as the same thing as the EMF inside the power source. This is case 1 above.

When the power source is connected to something with finite resistance the voltage drops according to both (1) the amount of internal resistance in the power source prior to the output terminals, and (2) the amount of current drawn by the load. This is case 2 above. Zero internal resistance, or infinite external load, would mean that the terminal voltage is the same as the EMF, just as in case 1 above.