Level 3 Applied Technology

Sample Item

You are building a greenhouse like the one shown in Figure 1 for a local nursery. The owners specified that the greenhouse should have automatic vents, controlled by a thermostat, which will open when the temperature in the greenhouse gets too high for the plants. Figure 2 shows the floor plan of the greenhouse.

A thermostat will control the opening and closing of the automatic vents. It is a temperature-sensitive device that can be set to activate when the air around it reaches a certain temperature. The owners of the greenhouse want to have the vents open when the air around the majority of the plants reaches 90°F. At what height and location in Figure 2 should you install the thermostat so it gives the desired results?

1. About 4 feet from the floor at location A
2. About 4 feet from the floor at location B
3. About 8 feet from the floor at location C
4. About 8 feet from the floor at location D
5. Near the peak of the roof at location E

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Why this is a Level 3 item:

• The problem focuses on a simple system involving three major components: (1) a greenhouse, (2) automatic vents, and (3) a thermostat.
• The problem is straightforward: locate the thermostat 4 feet from the ground at location B.
• All the information needed to solve the problem is provided: the diagrams show the location of the vents and the configuration of the inside of the greenhouse.
• The examinee must understand the movement of heat (thermodynamics) and the function of the thermostat to solve the item: Location B is the center most part of the greenhouse and is at plant height. Locating the thermostat here will give the most accurate temperature reading for the majority of the plants.

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