Which one of the following is the lowest possible temperature?
- (a)0° Celsius
- (b)–073° Celsius
- (c)–173° Celsius
- (d)–273° Celsius
Correct — D, −273 °C. The lowest possible temperature is absolute zero, which is about −273 °C (more precisely −273.15 °C) and defines the zero of the Kelvin scale (0 K). At this point the thermal motion of particles is at its theoretical minimum, so no temperature can be lower. The other values — 0 °C, −73 °C and −173 °C — are all above absolute zero and so are not the lowest possible.
- (a)0° Celsius — 0 °C is just the freezing point of water, far above the lowest possible temperature.
- (b)–073° Celsius — −73 °C (about 200 K) is cold but well above absolute zero.
- (c)–173° Celsius — −173 °C (about 100 K) is colder still, yet it is not the limit — temperature can fall further, to −273 °C.
Absolute zero is the theoretical lower limit of temperature, at which a system has minimum thermal energy; it corresponds to 0 kelvin, equal to about −273.15 °C. The Kelvin (absolute) scale begins here, and no temperature below absolute zero is possible.
The options are steps toward the limit (0, −73, −173, −273). Recall that absolute zero is about −273 °C (0 K) and pick the lowest, most negative value.
- Absolute zero is about −273.15 °C, equal to 0 K — the lowest possible temperature.
- The Kelvin scale is an absolute scale that begins at absolute zero.
- To convert, K = °C + 273.15 (approximately °C + 273).
- At absolute zero the thermal motion of particles is at its theoretical minimum.
The lowest possible temperature is absolute zero, −273 °C — option (d).
- Picking a cold-sounding but non-limiting value such as −173 °C.
- Confusing 0 °C (the freezing of water) with the lowest possible temperature.
Asked as 'lowest possible temperature' with progressively colder decoys — recall that absolute zero is about −273 °C (0 K).
UPSC_1995_GS1_Q1071995The normal temperature of human body on the Kelvin scale is
- (a) 280
- (b) 290
- (c) 300
- (d) 310
Answer(d) 310
Same concept — the absolute (Kelvin) temperature scale. That UPSC item converts body temperature to kelvin (K = °C + 273); this one tests where that scale starts, at absolute zero, −273 °C.
The temperature of a place on one sunny day is 113 °F on the Fahrenheit scale. The Kelvin scale reading of this temperature will be
- (a) 318 K
- (b) 45 K
- (c) 62·8 K
- (d) 335·8 K
Answer(a) 318 K
Same area — absolute temperature and scale conversion. That NDA item converts a Fahrenheit reading to the Kelvin scale; this one tests the zero point of that scale, absolute zero (−273 °C).
- practice — not a real PYQ
Absolute zero on the Celsius scale is approximately
- (a)0 °C
- (b)−100 °C
- (c)−273 °C
- (d)−373 °C
Answer(c) −273 °C — equal to 0 K.
- practice — not a real PYQ
The zero of the Kelvin scale corresponds to
- (a)freezing point of water
- (b)boiling point of water
- (c)absolute zero
- (d)room temperature
Answer(c) absolute zero — the lowest possible temperature.