Units and Measuring Instruments

A kilowatt-hour (kWh) is a unit of energy, representing the amount of energy consumed when a power of one kilowatt is used for one hour. It is not a unit of power, current, or time.

1 meter is equal to 100 centimeters because the prefix 'centi-' means one hundredth, so 100 centimeters make up 1 meter.

1 meter is equal to 1000 millimeters because 1 meter = 100 centimeters and 1 centimeter = 10 millimeters, so 100 × 10 = 1000 millimeters.

A Geiger counter is an instrument used to detect and measure ionizing radiation, commonly referred to as radioactivity. It does not measure pressure or water flow.

A fathom is a unit of length commonly used to measure the depth of water and is equal to 6 feet. This is a standard measurement in nautical contexts.

The Mohs scale is a scale of mineral hardness used to measure the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. Therefore, it is used to measure hardness.

A bolometer is an instrument used to measure the power of incident electromagnetic radiation via the heating of a material with a temperature-dependent electrical resistance. It effectively measures heat radiation.

One tonne is defined as 1000 kilograms. This is a standard unit conversion in the metric system.

The Beaufort Scale is the standard measurement scale used to estimate wind speed based on observed conditions, making it the correct answer. The Richter Scale measures earthquake magnitude, and 'Meter-second scale' is not a recognized scale for wind speed.

A velometer is an instrument used to measure the speed of air or wind. It is commonly used in meteorology and ventilation studies.

Pressure can be measured in various units including Barr (likely intended as Bar), Torr, and Pascal. Therefore, all the options listed are valid units of pressure.

The activity of the brain is recorded by an EEG (Electroencephalogram), which measures electrical activity in the brain. ECG records heart activity, X-Ray is used for imaging bones and other structures, and 'None of these' is incorrect.

One carat is internationally defined as exactly 0.2 grams, which is the standard unit of mass used for gemstones and pearls.

Blood sugar levels are commonly measured in milligrams per deciliter (mg/dL), which indicates the concentration of glucose in the blood. This is the standard unit used in most medical settings.

A nanometer (nm) is defined as one billionth of a meter, which is 10 to the power of -9 meters. Therefore, 1 nanometer equals 10^-9 meters.

BTU (British Thermal Unit) is a unit of energy commonly used to measure heat. It represents the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit.

A pyrometer is an instrument specifically designed to measure very high temperatures, often in industrial settings, whereas a pyroscope is not a standard term for temperature measurement. Seismograph measures earthquakes, and xylometer is not related to temperature measurement.

An anemometer is the instrument specifically designed to measure wind speed, whereas a barometer measures atmospheric pressure, a hydrometer measures liquid density, and a hygrometer measures humidity.

A hygrometer is an instrument specifically designed to measure the humidity or moisture content in the air, making option C the correct answer.

A pyrometer is an instrument specifically designed to measure very high temperatures, often in industrial settings. The other options measure different parameters: a manometer measures pressure, a thermostat regulates temperature, and a chronometer measures time.

A lactometer is a specialized hydrometer designed specifically to measure the specific gravity of milk, which helps determine its purity and quality.

A chronometer is an instrument designed to measure time very precisely, often used in navigation and scientific experiments. Therefore, the correct answer is 'Time'.

A lactometer is specifically designed to measure the purity and density of milk, helping to detect adulteration. The other instruments measure different properties: a hygrometer measures humidity, a manometer measures pressure, and a sonometer measures sound frequency.

A stereoscope is an optical instrument used to view two slightly different images of the same object, creating a perception of three-dimensional depth. This allows us to see three-dimensional pictures, unlike the other options listed.

One gross is a unit of quantity equal to 12 dozen, which means 12 times 12, or 144 items. Therefore, option C (12 Dozen) is correct.