s. (a) Electrolytic Cell (b) Galvanic Cell or Voltaic Cell Electrolytic Cell: It is a device in which electrolysis (chemical reaction involving oxidation and reduction) is carried out by using electricity or in which conversion of electrical energy into chemical energy is done. Galvanic Cell: The device used to convert the chemical energy produced on a red-ox reaction into electrical energy is called an electrochemical cell or simply a chemical cell. These are also called galvanic cells or voltaic cell after the names of Luigi Galvanic and Alessandro Volta who were first to perform experiments on the conversion of chemical energy into electrical energy. In electrochemical cell, a spontaneous red-ox reaction is carried out in an indirect manner and the decrease in free energy during chemical reaction appears as electrical energy. An indirect red-ox reaction is such that reduction and oxidation processes are carried out in two separate vessels called half-cells. Daniel Cell: It consists of two half-cells. The left hand half-cell contains a zinc metal electrode dipped in ZnSo4 solution. The half-cell on the right hand side consists of Cu metal electrode in a solution of CuSo4. A salt bridge that prevents the mechanical mixing of the solution joins the half-cells. When the zinc and copper electrodes are joined by a wire the following observation are made. (a) There is flow of electric current through the external circuit. (b) The Zn rod loses its mass while copper rod gains in the mass. (c) The concentration of ZnSo4solution increases while the concentration of CuSo4 solution decreases. (d) The solutions in both the compartments remain electrically neutral. During the passages of electric current through external circuit, electrons flow from zinc electrode to the copper electrode. At the zinc electrode, zinc metal is oxidized to zinc ions, which go into the solution. The electrons released at the electrode travel through the external circuit to the copper electrode where they