The device used to measure atmospheric pressure is called a ______.

• A. Barometer
• B. Thermometer
• C. Altimeter
• D. Hygrometer

Answer: (A)

Measuring atmospheric pressure is done with a barometer. A barometer is designed to quantify the pressure exerted by the air surrounding us. In a traditional mercury barometer, the atmosphere pushes on a reservoir of mercury, supporting a column of mercury in a glass tube. When air pressure increases, the column is pushed higher; when pressure drops, the column falls. Modern versions use an aneroid mechanism—a sealed, flexible chamber with springs—that moves a dial or needle to indicate pressure. The reading tells weather conditions and is essential for aviation planning.

The other instruments measure different properties: a thermometer measures temperature, a hygrometer measures humidity, and an altimeter uses atmospheric pressure to estimate altitude rather than directly measuring pressure.