ANS:B - Wet bulb

The wet bulb temperature is a crucial meteorological and thermodynamic concept used to assess the humidity and cooling potential of air. Here's an explanation of wet bulb temperature:

1. Measurement Method: Wet bulb temperature is typically measured using a thermometer known as a wet bulb thermometer. This thermometer consists of a thermometer bulb covered with a moistened wick. As air passes over the wetted wick, water evaporates from the wick, causing the temperature of the bulb to decrease. The temperature indicated by the wet bulb thermometer is the wet bulb temperature.
2. Evaporative Cooling: The wet bulb temperature represents the lowest temperature that can be achieved through the process of evaporative cooling under specific conditions. When water evaporates from the wetted wick, it absorbs heat from the surrounding air, causing a decrease in temperature. This cooling effect occurs because energy is required to break the bonds between water molecules and convert liquid water into water vapor.
3. Relationship to Relative Humidity: The wet bulb temperature is influenced by the humidity of the air. In an environment with high humidity (close to saturation), evaporation is less effective because the air already contains a significant amount of water vapor. As a result, the wet bulb temperature will be closer to the dry bulb temperature (the temperature of the air) in humid conditions. Conversely, in dry conditions (low humidity), evaporation is more efficient, leading to a greater cooling effect and a larger difference between the wet bulb and dry bulb temperatures.
4. Psychrometric Charts: Wet bulb temperature is often used in conjunction with dry bulb temperature to analyze air conditions on psychrometric charts. These charts plot various properties of moist air, such as temperature, humidity, and enthalpy, allowing engineers and meteorologists to assess conditions related to heating, cooling, and humidity control.
5. Applications: Wet bulb temperature is utilized in various fields, including meteorology, HVAC (Heating, Ventilation, and Air Conditioning) engineering, and agriculture. It is particularly important in determining the cooling potential of evaporative cooling systems and assessing heat stress conditions for humans and animals.