Final answer:
During the heating cycle, the indoor coil becomes a condenser coil.
Step-by-step explanation:
During the heating cycle, the indoor coil becomes a condenser coil. The electrically driven compressor raises the temperature and pressure of the gas and forces it into the condenser coils that are inside the heated space.
Because the temperature of the gas is higher than the temperature inside the room, heat transfer to the room occurs and the gas condenses to a liquid. The liquid then flows back through a pressure-reducing valve to the outdoor evaporator coils, being cooled through expansion.