Mercury Barometer

Definition

A mercury barometer is a device used to measure atmospheric pressure. It consists of a glass tube filled with mercury that is inverted and immersed in a mercury reservoir. The height of the mercury column in the tube is directly proportional to the pressure of the surrounding air, providing a reliable way to measure changes in atmospheric pressure.

5 Must Know Facts For Your Next Test

1. The mercury barometer was invented by Evangelista Torricelli in 1643, who demonstrated that the height of the mercury column was inversely proportional to the atmospheric pressure.
2. The Torricellian vacuum at the top of the mercury barometer tube is considered one of the first practical demonstrations of the existence of a vacuum in nature.
3. Mercury barometers are highly accurate and sensitive, capable of detecting even small changes in atmospheric pressure, making them useful for weather forecasting and scientific research.
4. The standard unit of measurement for atmospheric pressure using a mercury barometer is the millimeter of mercury (mmHg) or the inch of mercury (inHg).
5. Mercury barometers are less commonly used today due to the toxicity of mercury, and have been largely replaced by more modern, digital barometers that use alternative pressure-sensing technologies.

Review Questions

• Explain how a mercury barometer works to measure atmospheric pressure.
  • A mercury barometer works by using the weight of the mercury column in the glass tube to directly measure the pressure of the surrounding air. As atmospheric pressure increases, the mercury is pushed up the tube, and as pressure decreases, the mercury level falls. The height of the mercury column is inversely proportional to the atmospheric pressure, allowing the barometer to provide a reliable and accurate reading of the air pressure at a given location.
• Describe the significance of the Torricellian vacuum in the mercury barometer and its historical importance.
  • The Torricellian vacuum at the top of the mercury barometer tube is a crucial component of the device. This empty space, created by the weight of the mercury column, was one of the first practical demonstrations of the existence of a vacuum in nature, which was a groundbreaking discovery at the time. The creation of the Torricellian vacuum helped establish the principles of atmospheric pressure and the behavior of gases, laying the foundation for the development of modern physics and meteorology.
• Analyze the advantages and disadvantages of using a mercury barometer compared to more modern pressure-sensing technologies.
  • Mercury barometers offer high accuracy and sensitivity in measuring atmospheric pressure, making them valuable tools for weather forecasting and scientific research. However, they also have significant drawbacks, such as the toxicity of mercury, which has led to their replacement by more modern, digital barometers. These newer technologies often use alternative pressure-sensing methods, such as electronic sensors or aneroid mechanisms, which are safer, more compact, and often more affordable than traditional mercury barometers. While mercury barometers remain useful in some specialized applications, the shift towards digital barometers has made pressure measurement more accessible and environmentally friendly.

Related terms

Atmospheric Pressure: The force exerted by the weight of the air molecules in the Earth's atmosphere on a given surface area.

Torricellian Vacuum: The empty space at the top of a mercury barometer tube, created by the weight of the mercury column.

Barometric Pressure: The pressure exerted by the weight of the atmosphere at a given point, as measured by a barometer.