The correct answer is: A. Local atmospheric pressure depends upon elevation of locality only.
Explanation:
Atmospheric pressure is the force exerted by the weight of the air above a given point on Earth’s surface. It is measured in units of millibars (mb) or inches of mercury (Hg). The average atmospheric pressure at sea level is 1013.25 mb or 29.92 inches of Hg.
The atmospheric pressure at a given location is affected by several factors, including the elevation of the location, the temperature of the air, and the amount of water vapor in the air. The higher the elevation, the lower the atmospheric pressure. This is because there is less air above a given point at higher elevations. The temperature of the air also affects atmospheric pressure. Warm air is less dense than cold air, so it exerts less pressure. The amount of water vapor in the air also affects atmospheric pressure. Water vapor is lighter than air, so it exerts less pressure.
A barometer is an instrument used to measure atmospheric pressure. There are two main types of barometers: mercury barometers and aneroid barometers. Mercury barometers use a column of mercury to measure atmospheric pressure. Aneroid barometers use a sealed chamber that is evacuated of air. The chamber is connected to a spring, and the change in the pressure of the air in the chamber causes the spring to move. The movement of the spring is then used to measure the atmospheric pressure.
The following are the incorrect statements and their explanations:
- Statement B: Standard atmospheric pressure is the mean local atmospheric pressure at sea level. This is not true. Standard atmospheric pressure is the average atmospheric pressure at sea level at a latitude of 45 degrees north or south.
- Statement C: Local atmospheric pressure is always below standard atmospheric pressure. This is not true. Local atmospheric pressure can be above or below standard atmospheric pressure, depending on the factors mentioned above.
- Statement D: A barometer reads the difference between local and standard atmospheric pressure. This is not true. A barometer reads the atmospheric pressure at a given location.