P shows a basic schematic of how an airbrush works. In the options, the green sections are seals. Of these options, which of the design concepts of an airbrush will work continuously until the liquid in the container is exhausted up to the dotted line?
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When analyzing a functional design based on a physical principle, first identify the core requirements for the principle to work. In this case (Venturi effect), it's the pressure difference and a continuous supply path. Evaluate each option against these fundamental requirements.
Step 1: Understanding the Concept:
The question is about the functional design of an airbrush based on the Venturi effect, as shown in diagram P. For the airbrush to work, high-speed air flowing over the top of a straw must create a low-pressure zone, allowing atmospheric pressure on the liquid's surface to push the liquid up the straw. Two conditions are critical for continuous operation until the liquid is nearly gone:
The container must be sealed to maintain the pressure difference.
The straw must be long enough to reach the bottom of the liquid supply (i.e., near or below the dotted line).
Step 2: Detailed Explanation:
Let's evaluate each design option based on these two criteria.
Option A: The straw is too short. It does not reach the dotted line. The airbrush will stop working as soon as the liquid level drops below the end of the straw.
Option B: The straw is also too short. It will stop working long before the liquid is exhausted up to the dotted line.
Option C: The straw is long enough, extending to the bottom of the container, well below the dotted line. The green seal is placed on the outside of the container's neck, which can provide an effective airtight seal. This design will work continuously.
Option D: The straw is long enough, reaching the bottom of the container. The green seal is placed on the inside of the neck, functioning as a stopper, which also provides an effective airtight seal. This design will also work continuously.
Step 3: Final Answer:
Both options C and D have straws that are long enough to draw liquid until it is exhausted and have effective seals to maintain the necessary pressure differential. Therefore, both designs will work as required.
