Final answer:
The positive electrode in an electrotherapy device is called the cathode. In a galvanic cell, the cathode is where reduction occurs and is positive, while the anode is negative and where oxidation occurs.
Step-by-step explanation:
The positive electrode in an electrotherapy device is called the cathode. In the context of electrochemical cells, each electrode has a specific role in the redox reactions that occur. The electrode at which oxidation happens is termed as the anode, and is negatively charged, while the cathode is where reduction occurs, therefore becoming the positive electrode. Galvanic (or voltaic) cells and electrolytic cells differ in their charge designations - in a galvanic cell, the anode is negative, but in an electrolytic cell, the situation is reversed, with the anode becoming positive.
For a given galvanic cell, if we were to write the half-reactions:
- The anode half-reaction would involve the loss of electrons (oxidation).
- The cathode half-reaction would involve the gain of electrons (reduction).
Therefore, using this information, we can determine that the electrode labeled as the cathode would be the one increasing in mass (if the cell involves solid deposits forming, such as in copper plating), and it would be the positive electrode in the setup, while the anode would be negative.