Final answer:
Applying carburetor heat leads to a loss of power in aircraft engines because the warm air is less dense and contains less oxygen for combustion, reducing engine efficiency.
Step-by-step explanation:
The reason for a loss of power when carburetor heat is applied in an aircraft engine is due to the introduction of warm air from the carburetor heat system into the engine's air intake. Warm air is less dense than cold air, which means that there is less oxygen available for combustion in each intake stroke of the engine. This decrease in oxygen content reduces the efficiency of the combustion process, hence reducing the power output of the engine. The carburetor heat is used to prevent or clear any ice formation within the carburetor, which is essential for safety but comes at the cost of reduced engine performance.