The electrode potential measures the tendency of electrons to flow away from or towards a redox equilibrium. They are always measuredwith respect to the standard hydrogen electrode (which is assigned a value of zero volts).

In cell reaction :

Cu(s) +2Ag⁺(aq) ---->Cu²⁺(aq) +2Ag(s)

Half cell reaction
Cathode (reduction ):
2Ag⁺(aq) +2e^- -----> 2Ag(s)

Anode (oxidation)
Cu(s) -----> Cu²⁺(aq) +2e^-

 In overall reaction of the cell, silver electrode act as cathode and copper electrode act as anode.

A half-cell called standard hydrogen electrode
represented by Pt(s)l H₂(g)lH+(aq), is assigned
a zero potential at all temperatures corresponding to the reaction;

H⁺ (aq) + e^- ---->1/2H₂(g)

The standard hydrogen electrode consists of a platinum electrode coated with platinum black. The electrode is dipped in an acidic solution and pure hydrogen gas is bubbled through it.

A galvanic cell (left) transforms the energy released by a spontaneous redox reaction into electrical energy that can be used to perform work. The oxidative and reductive half-reactions usually occur in separate compartments that are connected by an external electrical circuit.

Oxidation half reaction:
Y ----> Y⁺ +e^-

Reduction half reaction:
Z + e^- ----> Z^-

overall cell reaction

Y+Z ------> Y⁺ + Z^- (G<0)

A second connection that allows ions to flow between the compartments (shown here as a vertical dashed line to represent a porous barrier) is necessary to maintain electrical neutrality. The potential difference between the electrodes (voltage) causes electrons to flow from the reductant to the oxidant through the external circuit, generating an electric current.

A salt bridge is a U-shaped device containing concentrated solution of an inert electrolyte like KCl, KNO3, etc.or a solidified solution of those electrolytes in agar-agar solution and gelatin. It connects the oxidation and reduction half-cells of a galvanic cell. The inert electrolytes present do not take part in redox reaction of the cell and dont react with the electrolyte that has been used.

As electrons leave one half of a galvanic cell and flow to the other, a difference in charge is built up. If no salt bridge were used, this increasing charge difference would eventually prevent further flow of electrons. The salt bridge solves these problems. It has two main functions:

1. To allow the flow of ions from one solution to another without mixing of the two solutions and completing the electrical circuit.

2. To maintain the electical neutrality of the solutions in the two half cells.