Explanation: In a magnetron, the high voltage (typically thousands of volts negative) is applied to the **cathode**. The cathode is a heated filament located at the center of the magnetron, which emits electrons. This high negative voltage creates a strong electric field between the cathode and the surrounding anode block (which is often at ground potential). This electric field, combined with an external magnetic field, forces the emitted electrons into a circular path, causing them to interact with resonant cavities in the anode and generate microwaves. The anode forms the outer structure and contains the resonant cavities; it is typically at ground or a lower positive potential relative to the very negative cathode. The waveguide is used to extract the generated microwave energy, not to apply high voltage. A plate cap is a term generally associated with older vacuum tubes, not a magnetron element for high voltage application.