← CDL Air Brakes – Complete Study Flashcards

CDL Commercial Drivers License General Knowledge Practice Test

Free 5-question sample test with instant feedback. See how ready you are.

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Sample Questions

Question 1

What is the purpose of the air compressor in an air brake system?

Answer: The air compressor pumps air into the storage tanks to build and maintain the air pressure needed to operate the brakes.

Question 2

What is the function of the air dryer in an air brake system?

Answer: The air dryer removes moisture and contaminants from the compressed air before it enters the storage tanks, preventing freeze-ups and corrosion.

Question 3

What does the governor control in an air brake system?

Answer: The governor controls when the air compressor pumps air by cutting out at a set maximum pressure and cutting in again when pressure drops to a minimum level.

Question 4

At what pressure does the governor typically cut out the air compressor?

Answer: The governor cuts out the air compressor at approximately 125 psi (the cut-out pressure), stopping compression until pressure drops back to the cut-in level.

Question 5

What is the purpose of the safety relief valve in the air tank?

Answer: The safety relief valve opens to release air if the pressure in the tank exceeds the maximum safe level (usually 150 psi), protecting the system from over-pressurization.