Temperature — Set 5
Physics · तापमान · Questions 41–50 of 50
Absolute zero is approximately what value on the Fahrenheit scale?
Correct Answer: C. -459.67°F
Absolute zero corresponds to the zero of the kelvin scale. Converting that to Fahrenheit gives about -459.67°F. This is the theoretical lowest temperature limit in classical thermodynamics.
Mercury thermometers are not suitable for very low temperatures mainly because mercury freezes near which temperature?
Correct Answer: A. -39°C
Mercury freezes near about -39°C, so it cannot remain liquid below that. A thermometer needs the working fluid to stay in the same phase. Alcohol can be used for lower temperatures because it freezes much later.
In a constant volume gas thermometer, temperature is determined by observing the change in which quantity?
Correct Answer: D. Pressure of the gas
At constant volume, the pressure of a gas changes with temperature. Measuring the pressure gives a way to infer temperature. This method can be very accurate and is used for calibration standards.
What does thermal equilibrium between two bodies in contact mean?
Correct Answer: A. No net heat flows between them
Thermal equilibrium means there is no net heat transfer between the bodies. This happens when their temperatures are equal. The zeroth law uses this idea to define temperature comparison.
Convert 50°C to degrees Fahrenheit.?
Correct Answer: C. 122°F
Use F = (9/5)C + 32 for Celsius to Fahrenheit conversion. For 50°C, (9/5)×50 = 90 and 90 + 32 = 122°F. This shows the Fahrenheit value increases faster because of the larger scale factor.
An optical pyrometer is mainly used to measure temperature of objects in which situation?
Correct Answer: C. Very hot furnaces without contact
An optical pyrometer measures very high temperatures by analyzing emitted radiation. It works without touching the hot object. This is useful for furnaces and molten materials where contact is unsafe.
Water freezes at approximately what temperature on the kelvin scale under standard pressure?
Correct Answer: C. 273 K
Freezing point of water is 0°C under standard pressure. Adding 273.15 gives about 273 K on the kelvin scale. This is a commonly used reference temperature in basic thermometry.
Which statement about temperature differences on kelvin and Celsius scales is correct?
Correct Answer: D. A change of 10 K equals a change of 10°C
The correct answer is 'A change of 10 K equals a change of 10°C'. Kelvin and Celsius have the same size of temperature step. So a difference of 10 K is the same as a difference of 10°C. Only the zero points of the two scales are different.
Convert -10°C to kelvin (approximately).?
Correct Answer: B. 263 K
Convert Celsius to kelvin by adding 273.15. So -10 + 273.15 equals 263.15 K, about 263 K. Kelvin values remain positive for many subzero Celsius temperatures.
Which instrument measures temperature using the change of electrical resistance of a platinum wire?
Correct Answer: D. Platinum resistance thermometer
A platinum resistance thermometer uses the change in resistance of platinum with temperature. Platinum is chosen because it is chemically stable and gives repeatable results. This method is widely used for precise temperature measurement.