Final answer:
The electrically driven compressor is the component that energizes auxiliary heat during the defrost cycle of a heat pump.
Step-by-step explanation:
The component responsible for energizing auxiliary heat during the defrost cycle of a heat pump is the electrically driven compressor. During the defrost cycle, the compressor works to increase the temperature and pressure of the refrigerant gas. When a heat pump enters the defrost mode, it essentially operates in cooling mode, temporarily reversing the flow of refrigerant to melt any frost or ice built up on the outdoor coil. The compressor's role is to heat the refrigerant, which in turn melts the ice, and when heat is necessary to maintain comfort indoors, the auxiliary heat, warmed by the compressor, is engaged to supplement the heat pump's heating capabilities.