Electromotive Force or E.M.F of a Cell

The E.M.F of a cell is the algebraic difference between two electrodeElectrodes are conductors, in the form of wires, rods or plates, through which current enters and leaves the electrolyte. When the current leaves the electrodes it is known as the cathode... More potentials.

Thus the E.M.F of the cell (E^θ total), if formed by the system Zn_(s)/ Zn_(aq)// Cu²⁺ _(aq) / Cu_(s) is defined as the standard electrode potential of the left-hand electrode or oxidation electrode – reduction electrode e.g.  Zn_(s) / Zn_(aq) // Cu²⁺_(aq)/ Cu_(s)

E^θ Total = Standard electrode potential of the right-hand side (RHS) – Standard electrode potential of the left-hand side (LHS) 

E^θ Total = E^θ (RHS) – E^θ (LHS) 

Or

E^θ Total = E^θ (Red) – E^θ (0xd)

Thus if we have a cell represented as:

Zn_(s)/ Zn²⁺_(aq) // Cu²⁺_(aq) / Cu_(s)

(- 0.76 V)           (+0.34 V)