| English | Manometer |
|---|---|
| Bahasa Melayu | Manometer |
| 中文 | 压强计 |
Definition
A U-shaped tube containing liquid used to measure the pressure of a gas by comparing liquid levels in its two arms.
In exam terms
A manometer is a U-shaped tube containing a liquid, used to measure the pressure of a gas supply by comparing the liquid levels in its two arms. One arm is connected to the gas and the other is open to the atmosphere.
The gas pressure is found from the difference in liquid levels, h, using the liquid column pressure hρg (where ρ is the liquid density in kg m⁻³ and g is in N kg⁻¹). If the gas pushes the liquid down on its side so the open side is higher by h, then gas pressure = atmospheric pressure + hρg.
Example sentence of correct use: The manometer shows a level difference of 0.15 m, so the gas pressure is greater than atmospheric pressure.
Do not confuse it with a barometer
Do not confuse a manometer with a barometer. A barometer, usually a mercury column in a tube closed at the top with a vacuum above, measures atmospheric pressure directly.
A manometer measures the pressure of a connected gas supply relative to the atmosphere, using the difference in levels between its two open arms.
In Paper 2 this is often asked as determine the gas pressure from a manometer diagram, or state whether the gas pressure is above or below atmospheric pressure by comparing which arm is higher. Remember to add the atmospheric pressure and the column pressure hρg together for the gas side.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)