Question

The instrument used to measure humidity of air is called:
(A) Calorimeter
(B) Hygrometer
(C) Pyrometer
(D) Hydrometer

Answer 1

Hint it is a theory based, for such a question you must know all measurable quantities with their respective units and instruments and methods which used to measure them. And what are the uses of measurement of such quantities? Humidity is the measure of concentration of water vapor present in the air.

Complete step by step answer: As you read humidity is the measure of concentration of water vapor present in the air. Humidity implies the precipitation, dew, or fog which is to be present. The amount of water vapor required to achieve saturation increases with the increases in temperature. As the temperature of air decreases it will suddenly reach the saturation point without adding or losing water mass.

Humidity is measured in three types:
(1) Absolute humidity describes the water content of air and is expressed in either grams per cubic meter or grams per kilogram.
(2) Relative humidity can be expressed as a percentage, which indicates a present state of absolute humidity relative to a max humidity that is given the same temperature.
(3) Specific humidity is the ratio of water vapor mass to total moist air parcel mass.

A hygrometer is an instrument which used to measure the amount of water vapor in air, soil, or confined spaces. Humidity measurement instruments usually depend on measurements of some other quantities like pressure, mass, temperature, a mechanical or electrical change in a substance as moisture is absorbed.

Hence option B is correct.

Note Other such important quantities and instruments used to measure them are:
(1) A thermometer is an instrument which is used to measure temperature.
(2) An anemometer is a weather instrument that measures wind speed.
(3) A rain gauge is an instrument which is used to measure the amount of liquid precipitation over a certain period of time.
(4) Barometers are used to measure Atmospheric pressure.