Question

Briefly describe the working of a simple barometer.

Answer 1

Hint: A barometer is a device that is used to measure atmospheric pressure. It can also be used to measure altitude or height, because atmospheric pressure changes with change in distance from the sea level. The atmospheric pressure measured by the barometer is known as barometric pressure.

Complete solution:
Step I: A barometer consists of a glass tube which has one end open and the other end is sealed. The tube is filled with mercury. The open end is then inverted and it is then placed into an open reservoir of mercury.

Step II: Because of the presence of vacuum in the tube, the tube will not get completely empty and some amount of mercury will be there. Therefore, the pressure inside the tube gets balanced with the atmospheric pressure outside the tube.

Step III: When the pressure outside the tube gets lowered, then the resulting pressure on the mercury in the reservoir will also low down. This is because more mercury will be empty from the tube. On the contrary, when the pressure outside the tube increases, the pressure inside the tube also increases and forces a little mercury in the tube. This raises the level of mercury in the tube.

Note: It is important to remember that there are two main types of barometers. One is a mercury barometer and the other is an android barometer. In an aneroid barometer, the atmospheric pressure is measured by using the expansion of a metal. But in a mercury barometer, the height of mercury is adjusted to measure atmospheric pressure.