MTTC Secondary Integrated Science Practice Test 2026 – The All-in-One Guide to Ace Your Michigan Teacher Certification!

A hair hygrometer functions by observing the contraction and expansion of human or animal hair in response to changes in humidity levels. Hair is made up of proteins that interact with moisture in the air; as the humidity increases, the hair absorbs water and expands. Conversely, when the humidity decreases, the hair loses moisture and contracts. This physical change in the length of the hair can be measured and used to indicate the relative humidity of the environment.

The other options do not represent the mechanism behind a hair hygrometer. Measuring air pressure changes would pertain to barometers, while gauging temperature difference involves thermometers, and tracking wind direction refers to devices such as wind vanes or anemometers. Each of these instruments serves a different purpose and operates based on different physical principles.