Atmospheric pressure is measured by which instrument?
- A.Hygrometer
- B.Barometer
- C.Anemometer
- D.Lactometer
Correct answer
Explanation
The correct answer is B, barometer. A barometer measures the pressure of the atmosphere, traditionally by balancing it against a column of mercury. It is also used for forecasting weather, because a sudden drop in pressure signals an approaching storm, and for finding altitude, since pressure falls as one rises.
Option A, the hygrometer, measures the humidity of the air. Option C, the anemometer, measures the speed of the wind and is the cup-shaped device seen at weather stations. Option D, the lactometer, checks whether milk has been diluted, by measuring its relative density. Keep the confusing pair apart: hygrometer for humidity and hydrometer for the density of a liquid. The mercury barometer was invented by Evangelista Torricelli, and the aneroid barometer, which uses a sealed metal box instead of a liquid, is the portable form carried on aircraft and used as an altimeter. Pressure itself is measured in pascals, and one atmosphere is about 1.013 lakh pascals.
Read the full article: Units and Measurements: SI Units, Dimensions and Instruments
Practice Questions
View allWhat is the SI unit of force?
- A.Joule
- B.Newton
- C.Watt
- D.Pascal
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One newton is the force that gives a mass of one kilogram an acceleration of one metre per second squared, which follows directly from the equation force equals mass times acceleration.
Read the full explanation →How many base units are there in the International System of Units (SI)?
- A.Five
- B.Six
- C.Seven
- D.Nine
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The SI system, adopted in 1960 by the General Conference on Weights and Measures, rests on seven base units: the metre, the kilogram, the second, the ampere, the kelvin, the mole and the candela.
Read the full explanation →Which one of the following is NOT a base unit of the SI system?
- A.Kelvin
- B.Mole
- C.Newton
- D.Candela
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The newton is a derived unit: it is built from the kilogram, the metre and the second, since force equals mass times acceleration, and it can be written as one kilogram metre per second squared.
Read the full explanation →The candela is the SI unit of which physical quantity?
- A.Luminous intensity
- B.Electric current
- C.Amount of substance
- D.Pressure
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The candela takes its name from the candle, which was once used as a rough standard of light, and it is one of the seven base units of the SI system.
Read the full explanation →A light year is a unit of which of the following?
- A.Time
- B.Distance
- C.Speed
- D.Brightness of a star
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A light year is the distance that light, moving at about three lakh kilometres per second, covers in one year, which works out to roughly 9.46 trillion kilometres.
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