Question 483General Subjects - Assistant Engineer

The correct answer is B) When the air is completely saturated with moisture and the relative humidity is 100%. When the air is completely saturated with moisture, meaning the relative humidity is 100%, the dry bulb, wet bulb, and dew point temperatures will all be equal. This is because under these conditions, the air cannot hold any more moisture, and the temperature at which water vapor starts to condense (the dew point) is the same as the actual air temperature (the dry bulb). The other options are incorrect because: A) 0% relative humidity means the air is completely dry, not saturated; C) zero grains of moisture per pound of dry air would mean the air is completely dry, not saturated; and D) it is possible for the three temperatures to be equal, specifically when the air is 100% saturated.