Question

State and explain four major defects in a simple barometer.

Answer 1

The major defects in a simple barometer are discussed below.

Meniscus formation

1. At the glass-mercury interface, cohesive forces predominate the adhesive forces which result in meniscus formation at the top of the glass tube.
2. Due to meniscus formation, the free surface of the mercury in the bowl does not coincide with the zero mark which causes an error in the readings.

Inconvenient to move

1. It is not convenient to shift a simple barometer from one place to another place.
2. Mercury in the simple barometer spills when shifted from one place to another place.

Orientation issues

1. It is way too difficult to keep the barometer tube in a vertical position.
2. If the simple barometer tilts a bit, there occurs an error in the readings and the atmospheric pressure obtained varies from the actual value.

Contamination of mercury

1. The mercury in the simple barometer is exposed to the atmosphere and there is every chance of impurities getting dissolved in it.
2. Due to the contamination of mercury by various impurities, the density of the mercury changes.
3. Due to the change in density of mercury, there occurs an error in the readings obtained and the atmospheric pressure measured varies from the true atmospheric pressure.