Final answer:
The red, positive electrode on a galvanic machine is the cathode, where the reduction half-reaction takes place, increasing the electrode's mass and completing the cell's circuit.
Step-by-step explanation:
The red, positive electrode on a galvanic machine is the cathode. In a galvanic or voltaic cell, a redox reaction occurs spontaneously, allowing for useful electrical work to be extracted. In such a cell, oxidation occurs at the anode (which is the negative electrode), and reduction occurs at the cathode (which is the positive electrode). The cathode gains mass over time due to the deposition of metal during the reduction process, which means that ions from the solution are reduced to form a solid metal on the electrode, as seen in the provided example involving copper reduction.
In a typical galvanic cell arrangement, two electrodes are placed in different solutions connected by a salt bridge, or they can be immersed in the same solution without the need for a salt bridge if measuring voltage across a single electrolyte solution. The movement of electrons from the anode to the cathode through an external circuit generates an electric current, transforming chemical energy into electrical energy. The red, positive electrode or cathode is where the reduction half-reaction takes place, completing the circuit of the cell.