Voltaic cells are used as a source of electrical power. By their nature, they produce direct current.
A voltaic cell, or galvanic cell is an electrochemical cell that uses a chemical reaction to produce electrical energy. The cell consists of two metals: one called anode where oxidation (loss of electrons) occurs and the other cathode where reduction (gain of electrons) occurs.The salt bridge connect the anode with the cathode. It is the chamber of electrolytes necessary to complete the circuit in a voltaic cell.
The external circuit is used to conduct the flow of electrons between the electrodes of the voltaic cell and includes a load.
The key to gathering the electron flow is to separate the oxidation and reduction half-reactions, connecting them by a wire, so that the electrons must flow through that wire.