In a recharging battery, or an electrolytic cell, the cathode is the negative terminal, which sends current back to the external generator.It is continued externally by electrons moving inwards, negative charge moving one way amounting to positive current flowing the other way. This outwards current is carried internally by positive ions moving from the electrolyte to the positive cathode (chemical energy is responsible for this "uphill" motion). In a discharging battery or galvanic cell (drawing) the cathode is the positive terminal, where conventional current flows out.
To dispel a common misconception, often incorrectly inferred from the correct fact that in all electrochemical devices positively charged cations move towards the cathode and/or negatively charged anions move away from it, cathode polarity is not always negative but depends on the device type, and sometimes even in which mode it operates, as determined by the above current direction based universal definition. Diagram of a copper cathode in a galvanic cell.Ī cathode is an electrode through which (positive) electric current flows out of a polarized electrical device.
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