Setting Up Galvanic Cells
A galvanic cell converts chemical energy into electrical energy by a process called redox reaction. Two metal strips are set up as electrodes immersed in salt solutions and are connected by a wire to allow electric current to flow.
The picture below shows a typical setup for galvanic cells. The left side cell shows oxidation half-cell (the anode) and the right side shows reduction half-cell (the cathode). Oxidation half-cell releases electrons to the reduction half-cell that receives the electrons. This flow of electrons is what produces the electric current flow.
The salt bridge is a porous disk necessary to maintain the charge neutrality of each half-cell solution. At first a small amount of electrons will flow from the anode to the cathode. Eventually, the charge will build up to the point that it will repel electrons and stop further electron flow.
The salt bridge provides non reactive salt ions to neutralize the solutions. This means that the half-cell solutions will not have a build up of charges and this encourages electrons to keep migrating from the anode to the cathode because of the electrical potential difference between the cells. When the materials are used up, the battery will then stop working.
The video below shows how a salt bridge works