Certified Associate Constructor (CAC) Level 1 Practice Exam

Air sample A has a dry bulb temperature of 80º F and a relative humidity of 90%. Air sample B has a dry bulb temperature of 65º F and a relative humidity of 90%. Which of the following statements is true?

A has more sensible heat but the same latent heat as B.

A has less sensible heat but more latent heat as B.

A has more sensible and latent heat as B.

To understand why the chosen answer is correct, it's important to consider the definitions of sensible heat and latent heat and how they relate to temperature and humidity levels in the two air samples.

Sensible heat is the heat energy that causes a change in air temperature without changing its moisture content. In contrast, latent heat refers to the energy absorbed or released due to changes in moisture content, influencing the humidity levels of the air.

Air sample A has a higher dry bulb temperature (80º F) compared to air sample B (65º F). This higher temperature implies that air sample A can hold more moisture before reaching saturation. Given that both samples have the same relative humidity of 90%, air sample A contains significantly more moisture in absolute terms than B because warmer air can hold more moisture.

Now, since air sample A has a higher temperature, it will also contain more sensible heat due to its higher thermal energy. In addition, since it has more moisture at a higher absolute level, it possesses more latent heat as well.

Therefore, the understanding that air sample A possesses both more sensible heat due to its higher temperature, and more latent heat because it can retain a greater amount of moisture at that temperature, justifies why air sample A has more of both

A has less sensible and latent heat as B.