Ans. POTENTIAL DIFFERENCE
The work which must be done between any two points against electric forces to move a unit charge form one point to the other is called potential difference.
ELECTROMOTIVE FORCE (e.m.f.)
Electromotive force is the total amount of energy supplied by the battery in moving one coulomb of positive charge from the negative to the positive terminal of the battery. .
Energy Thus emf =C Rirge-
W or "Q where E is e.m.f, W is energy and Q is positive charge.