FAA Jeppesen Instrument Rating Practice Test 2026 – Your Complete Exam Prep

The correct answer is based on the principle of how a venturi works in a carburetor. The venturi is designed with a narrowed section that creates a decrease in pressure as air flows through it. This phenomenon is a result of Bernoulli's principle, which states that an increase in the speed of a fluid occurs simultaneously with a decrease in pressure.

When air enters the carburetor and moves through the venturi, its velocity increases due to the reduced cross-sectional area. This increase in airspeed results in a corresponding drop in pressure in the venturi. As the pressure inside the venturi decreases, it creates a vacuum effect that pulls fuel from the fuel bowl into the airstream. This process is critical for the proper mixing of air and fuel, allowing the engine to run smoothly.

Other options do not directly create the vacuum necessary for fuel draw. For instance, while the throttle valve opening allows air to flow into the venturi, it does not create the low pressure itself; it simply regulates the amount of air entering. The fuel pump's pressure is crucial for delivering fuel to the carburetor, but it does not generate the vacuum for fuel flow through the venturi. External air pressure does influence the overall operation of