Physics Measuring Instruments

A chronometer is a precision timekeeping instrument, specifically designed for maritime navigation to determine longitude. While standard clocks can lose accuracy at sea due to temperature changes and motion, chronometers maintain precise timekeeping even on ships.

A commutator is a rotary switch in a dynamo/generator that reverses the current direction periodically, converting AC to DC in the external circuit. Voltmeters measure voltage, ammeters measure current, and keys are switches - none change current direction.

A barometer is the instrument specifically designed to measure atmospheric pressure. An altimeter measures altitude, a thermometer measures temperature, and 'pressure meter' is not a standard scientific instrument name for atmospheric pressure measurement.

A hydrometer is an instrument specifically designed to measure the specific gravity (relative density) of liquids. It works on Archimedes' principle - it floats higher in denser liquids. A hygrometer measures humidity, gravimeter measures gravitational field strength, and hypsometer measures altitude or determines boiling points.

A protractor is a semi-circular or circular tool marked with degree measurements used to measure and draw angles. A scale measures length, a compass draws circles, and a setsquare draws specific angles (90°, 45°, 60°).

An altimeter (note correct spelling) is an instrument used to measure altitude, typically in aviation and mountaineering. It works by detecting changes in atmospheric pressure which decreases with increasing elevation.

An anemometer is a device used for measuring wind speed.

This is the correct answer as sphygmomanometer is used to measure blood pressure.

An ammeter is specifically designed to measure electric current in a circuit. A galvanometer can detect current but requires a shunt to measure larger currents, while a voltmeter measures potential difference and an odometer measures distance.

A periscope uses mirrors or prisms to reflect light, allowing submarines to see above the waterline while submerged. Sonar detects objects using sound but provides no visual image, telescopes require direct line of sight, and gyroscopes measure orientation.

Hygrometers specifically measure atmospheric humidity (water vapor content). Hydrometers measure liquid density, barometers measure air pressure, and galvanometers measure electric current - none of these measure humidity.

Rheovibron is used for measuring Visco-elastic properties.

A sphygmomanometer is the medical instrument used to measure blood pressure. It consists of an inflatable cuff and a pressure gauge. Barometer measures atmospheric pressure, hydrometer measures liquid density - neither is used for blood pressure.

This is the correct option. The instrument to measure wind speed is called anemometer.

A sextant is primarily a navigation tool used to measure angular distances, particularly the altitude of celestial bodies above the horizon. Through triangulation principles, it can also help determine the height of objects. Options like area, breadth, and volume require different measurement tools entirely.