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Level 3 Applied Technology

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. 

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.
  1. 1.

    At what height and location in Figure 2 should you install the thermostat so it gives the desired results?

    Individual Question