Why does electromotive force not depend upon the distance between the electrodes of an electrochemical cell?

Question

I know that it does not depend upon the distance between the electrodes.I just want to know why it doesn't...Plz help !!!

Answer 1

EMF is a force field. This is not the same as voltage, which is a measure of potential.

A force field can be thought of as an area filled with mini force vectors. So f = F/A; where F is the total force at the source and A is the area over which that force is spread some distance R from the source. The f here is the EMF field (they call it a field because the mini vectors are spread over an area like grass is spread over a field of grass).

A for the surface of a sphere is = 4 pi R^2; so that f = F/4piR^2, which is why EMF, gravity, and any other force field that spreads out as a sphere from the source diminishes in strength according to the 1/R^2 rule. That is, the density of the mini force vectors decreases by 1/R^2; so the effective force (over a given object of area a) is decreased by that much from what it would have been at the source (R = 0 almost). This is why both Coulomb's Law and Newton's Gravity Law show 1/R^2 as a factor in determining force.

The voltage, V, on the other hand, does not diminish according to 1/R^2. In fact, there is no relationship between voltage and the distance between the two electrodes because voltage is a potential and not a force field. It is a potential because it represents the work it could do under the right conditions.

When the two electrodes are open, there is no current. And current is need to do work. When they are closed I = V/R; where R is the resistance of the thing that closes the circuit between the two electrodes. Current, I, flows and work, as measured by I^2 R or VI, is done. Thus, if R is fixed, no matter how far apart the electrodes might be, the same amount of work can be done whenever V is the same.

[NB: R is not necessarily fixed. Wire, for example, will have higher resistance for longer lengths (L) of wire. This results because R = kL; where k is a measure of resistance per linear measure, and L is the length of the wire. k is determined by the gauge of the wire and its composition.]

Answer 2

Becuase ,
Electromotive force = Energy transferred per unit charge.

It has no relation with distance .