They are very similar, but there is one key difference.
Both represent the change in energy (per unit charge) that a charged particle would experience if moving between two points.
The difference is that a potential difference usually refers to a static situation. In this case, if a charged particle moved from Point A and returned to Point A, the change in potential would be zero.
An EMF usually refers to a dynamic situation within a circuit -- ie, a looping conductor. In this case, a charge that went around such a circuit and ended up at its beginning point, would actually experience a change in energy.
Because an electromotive force is a potential difference (voltage) -specifically, an electromotive force is the open-circuit or no-load potential difference of a source such as a battery or generator.
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An electromotive force or potential difference between its ends.
-- potential difference -- electromotive force
an electromotive force or potential difference expressed in volts.
A measure of electromotive force is called voltage. It represents the potential difference between two points in an electrical circuit and is typically measured in volts (V).
Electromotive force (potential difference, voltage) between two points of a conductor.
'Voltage' is simply another term for 'potential difference', and an electromotive force is the open-circuit, or no-load, potential difference of a source such as a battery or generator.
Electrical potential refers to the electric potential energy per unit charge at a point in an electric field, measured in volts. Electromotive force (emf) is the energy per unit charge supplied by a source of electrical energy, such as a battery, to drive current through a circuit, also measured in volts. Essentially, electrical potential is a property of a point in the field, while emf is the force that drives the flow of charge.
EMF (electromotive force) is more useful, in fact vital, for any electrical or electronic circuit. At school level your teacher would not make a distinction (and probably doesn't know the difference, or even realise there is one) between electromotive force and potential difference. In answer to a school question, it's potential difference.
Because they're the same thing.
electromotive force (abbreviation: EMF or emf)