A
cathode is the
electrode from which a
conventional current leaves a polarized electrical device. This definition is sometimes remembered using the
mnemonic CCD for
cathode current departs. A conventional current describes the direction in which positive electronic charges move. Electrons have a negative charge, so the movement of electrons is opposite to the conventional current flow. Consequently, the mnemonic
cathode current departs also means that electrons flow into the device's cathode.