Question

When atmospheric pressure decreases, the diaphragm of Aneroid barometer

• A. Bulges out
• B. Bulges in
• C. Get depressed
• D. None

Answer 1

The correct option is A Bulges out

Aneroid barometers are popular for their light weight and size which increases its portability. The Aneroid barometer uses a small, flexible metal box called an aneroid cell (capsule). The evacuated capsule (or usually several capsules, stacked to add up their movements) is prevented from collapsing by a strong spring which is corrugated in form of a diaphragm. Small changes in external air pressure cause the cell to expand or contract. This expansion and contraction drives mechanical levers such that the tiny movements of the capsule are amplified and displayed on the face of the aneroid barometer. When atmospheric pressure increases, the spring in upper end of box gets depressed and the reading is thus visible due to the elastic potential energy stored in the spring due to compression.

When the pressure decreases, the diaphragm to which spring is attached bulges out, showing the reading in the opposite direction.