Humidity is essentially the quantity of water vapour in the atmosphere. We are surrounded by air that contains dew, fog, or other types of precipitation. This indicates how moist the air is. Simply explained, humidity is the quantity of water that is gaseous and present in the molecules of the air. Humidity is primarily determined by pressure and temperature. The air's humidity varies according to shifts in pressure and temperature in the region of concern.

Humidity Definition:-

It is the gaseous state of water vapours present in the air. It is defined under the consideration of temperature and pressure. The humidity in the air varies in accordance with changes in the system's or environment's temperature and pressure. When the amount of water vapour is the same, the amount of humidity will be higher at lower temperatures than it will be at higher temperatures.

Types of Humidity:-

There are three fundamental ways of measuring humidity. We may distinguish between three forms of humidity using the three methods of measurement humidity, they are as follows:

• Absolute Humidity

• Relative Humidity

• Specific Humidity

Absolute Humidity:-

Absolute humidity can be defined as the mass of water vapour content present in the air. In absolute humidity consideration of temperature is ignored.

Mathematically, absolute humidity is calculated as the mass of the water vapour divided by the volume of the air and water mixture, which is written as

Absolute Humidity = \frac{Mass of Water}{Volume of Air}

• Relative Humidity:-

Relative humidity of the air-water mixture is defined as ratio of the moisture in the air to the maximum amount that it can hold. The temperature is the only factor that influences how much moisture the atmosphere can hold.

Mathematically, relative humidity can be stated as:

Relative Humidity = \frac{Moisture In The Air}{Maximum Amount Of moisture Air Can Hold}

• Specific Humidity:-

The ratio of the mass of the vapour to the mass of the air that contains it is how specific humidity is calculated. As the temperature drops, so does the amount of vapour required to reach the saturation point. It might happen that the air parcel's temperature drops to a point where it reaches saturation without the need for any vapour mass. Similar to the mixing ratio is specific humidity.

Factors Affecting Humidity:-

There are two basic factors that affect and determine the concentration of humidity they are:-

• Temperature: - A fundamental element that controls both water evaporation and condensation is temperature. When all outside influences, such as wind, air, and sunshine, are completely ignored in an enclosed enclosure, the air in that space will, at a given temperature, contain a specific amount of water vapour.

Absolute Humidity \propto Temperature

Relative Humidity \propto\frac{1}{Temperature}

• Pressure: - The absolute pressure affects relative humidity in an enclosed system. When pressure is applied to an isothermal system with a constant temperature, the volume of the system naturally shrinks, raising the partial vapour pressure of the water molecules and, consequently, the system's relative humidity. The ideal gas equation is followed by the fluctuation in relative humidity that is connected to pressure.

Humidity \propto Pressure

Effects of Humdity

• In Plants and animals

Which animals and plants can thrive in a specific environment depends on the relative humidity. When the air has a high moisture content, the perspiration cannot evaporate. As a result, our bodies feel hot and sticky. In these circumstances, excessive sweating, increased blood circulation, and respiration control body temperature.

• Electronics

Electronic devices are designed to operate under specific humidity. During high humid conditions, the moisture may increase the conduction of permeable insulators leading to malfunction. Low humidity makes materials brittle. No matter the stated humidity range, condensation poses a serious risk to electronic devices. When an electronic device is transferred from a chilly environment, say a garage to a humid such as the house, condensation coats circuit boards and other insulators, short-circuiting the gadget. Low humidity favours the build-up of static electricity which results in the shutdown of computers when the discharge occurs.

• Industry

High humidity has a negative effect on the capacity of chemical plants that use furnaces as part of certain processes.