Galvanic cell

Overview
A Galvanic cell, also referred to as a Voltaic Cell, is an electrochemical cell that derives electrical energy from chemical reaction inside the cell. Galvanic cells typically contain an anode and cathode made from two different metals joined by a salt-bridge and separated by a porous membrane. A galvanic cell is a type of power-producing cell, more commonly referred to as a battery.

Technical Details
A Galvanic cell is composed from two half-cells separated by a porous membrane. In its simplest form, each half cell consist of a metal submerged in a salt of that metal. These salts are oxidation states of their base-metal, and the chemical reaction of an oxidation-reduction (redox) reaction. A salt bridge or porous membrane is used to separate the two solutions. The number of electrons transferred between the solutions must be equal.

As an example, the Daniell cell uses zinc and copper as the metals, while their respective salts are sulfates of each metal. Their electrical potential is the standard potential for the two half cells. In this case, the bridge allows SO42− ions to flow between the copper and zinc solutions, so that:


 * Cu2+ + 2e- Cu: E0 = +0.34 V
 * Zn2+ + 2e- Zn: E0 = −0.76 V

And thus the standard potential is:

+0.34 V − (−0.76 V) = 1.10 V