There are following differences

Electromotive Force (E.M.F)
The difference in the potential of two electrodes of a battery.
E.M.F is always greater than the potential difference between any points in the circuit.
Formula: E = I(R + r)
This is caused by the electric, gravitational and magnetic fields.
The electromotive force is the amount of energy given to each coulomb of charge.
 Potential Difference
Difference of potential between any two points on the circuit.
This is always less than the E.M.F
Formula: V = IR
This difference is only produced by the electric field.
The potential difference is the amount of energy utilized by one coulomb of charge.

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