How is power for the air conditioning pack obtained?

Power for the air conditioning pack is obtained by reducing the pressure of incoming bleed air. The air conditioning system in aircraft typically uses bleed air from the engines, which is high-pressure air extracted from the engine compressor section. By reducing the pressure of this bleed air, it allows the system to control the temperature and flow rate of the air that is distributed throughout the cabin.

The reduction in pressure not only enables the air conditioning system to function effectively but also allows it to create a cooling effect as the air expands and moves through the system. This process is essential for maintaining a comfortable environment for the crew and passengers, especially during long flights or in varying external temperature conditions.

The other options do not accurately reflect how the power for the air conditioning pack is generated. Increasing the pressure of outgoing air would not facilitate cooling; heating the incoming air would counteract the primary objective of the air conditioning system, and relying solely on ram air during flight does not provide the continuous and controlled environment needed for effective air conditioning inside the cabin.