The operating principle of float-type carburetors is based on which of the following?

• A. Thermal expansion of the float mechanism
• B. Difference in air pressure between the venturi and the float chamber
• C. Electrochemical reaction between fuel and air
• D. Catalytic conversion of fuel vapors

Answer: (B)

Verified step by step guidance

1. Understand that a float-type carburetor controls the fuel flow into the engine by maintaining a constant fuel level in the float chamber.
2. Recognize that the float mechanism rises or falls with the fuel level, opening or closing a valve to regulate fuel entering the chamber.
3. Identify that the key operating principle involves the difference in air pressure between the venturi (a narrowed section of the carburetor where air speed increases and pressure decreases) and the float chamber.
4. Know that this pressure difference causes fuel to be drawn from the float chamber into the air stream, mixing fuel and air for combustion.
5. Conclude that the correct principle is the difference in air pressure between the venturi and the float chamber, not thermal expansion, electrochemical reactions, or catalytic conversion.