Because the source of the energy stops, the electrical current stops -just as a light bulb turns off when you switch off the electricity running to it.

Because the source of the energy stops, the electrical current stops - just as a light bulb turns off when you switch off the electricity running to it.

It and reversing current different is not to be, but with a anode intermittently stop, because the intermittent power supply current interrupted, cathode potential with time periodically change.