EMF is electromotive force. PD is potential difference. I hope I'm interpreting this correctly. Potential difference is the difference in electric field potential between two charges some distance away from eachother. Absolute potential is what one usually sees in text books, as not often is potential energy between two point charges explained. Absolute potential is the amount of work (energy) required to move a positive test charge from infinity to some point near a point charge. Potential difference is merely the difference in potential from one point to another from that point charge, in the case of abs pot. It's relative to the point charge. So, if one is at, say, 120V abs pot from the point charge and moves the test charge closer to the point charge to, say, 130V, the potential difference is abs(130-120) = 10V. It's stating the amount of work that was required or expended to move the test charge. EMF basically is a potential difference generated from a chemical or induction source to push current around a circuit. In a circuit the potential differences from any charges must sum to zero. If they must sum to zero, how can current be pushed through a circuit? The answer is by the EMF. The work to transport a charge around a closed path, a circuit, in a net electric field from various point charges is zero since the closed path, the circuit, passes through the same point twice. Basically, it gains then loses all energy it gained when it comes back to the same point. So, the EMF compensates for this and adds energy to the circuit to transport current through the load and back to the negative side of the EMF. It's usually chemical or induction energy, as in a battery or a generator.
Potential difference is the voltage difference between any 2 points in a circuit. EMF is normally associated with the voltage across a generator phase.
Dear,
Thank you am also fine like you then dear origin is EMF where as difference between 2 EMF is name it as a potential difference.
Potential difference are more general. It doesn't consider from what the voltage comes from.
But emf comes from electric source such as generator, dynamo, thermoelectric generator, etc.
