The temperature of a body increases from 310 K to 340 K. The temperature increase in degree Celsius is
- (a)20°C
- (b)30°C
- (c)37°C
- (d)67°C
Correct — B, 30°C. A change (or interval) of temperature is the same number of degrees on the Kelvin and Celsius scales, because the two scales differ only by a fixed offset of 273.15 and have equal-sized divisions. So the increase is simply 340 − 310 = 30 K, which equals 30°C.
- (a)20°C — This is a wrong subtraction. 340 minus 310 is 30, not 20.
- (c)37°C — This converts the starting temperature to Celsius (310 K ≈ 37°C) instead of finding the increase. It answers the wrong question.
- (d)67°C — This converts the final temperature to Celsius (340 K ≈ 67°C) instead of finding the change. The rise is the difference of the two, which is 30°C, not the final value.
The Kelvin and Celsius scales measure temperature with divisions of exactly the same size; they differ only by a constant offset, since T(K) = t(°C) + 273.15. Because the step size is identical, a difference in temperature has the same numerical value in both scales.
The question separates an interval from an absolute reading. If you convert each end-point to Celsius (37°C and 67°C) you get the trap options; the increase is their difference, 30. The shortcut is to remember that a change of 1 K is a change of 1°C, so you can subtract directly in kelvin.
- A temperature difference of 1 K equals a difference of 1°C — the scales share the same division size.
- The scales are related by T(K) = t(°C) + 273.15, a fixed offset.
- The rise here is 340 − 310 = 30 K = 30°C.
- 310 K is about 37°C and 340 K is about 67°C, but those are the end-point temperatures, not the change.
- A change of temperature is identical in K and °C — subtract directly, do not add or remove 273.
- Do not confuse the end-point temperatures (37°C, 67°C) with the increase (30°C).
Temperature scales are tested by mixing intervals and absolute readings, so converting the wrong quantity lands you on a distractor.
The normal temperature of human body on the Kelvin scale is
- (a) 280
- (b) 290
- (c) 300
- (d) 310
Answer(d) 310
Same Kelvin–Celsius conversion skill. UPSC used normal body temperature (37°C, so 37 + 273 = 310 K); the NDA question uses the same 310 K value and tests that a temperature interval is identical in K and °C.
- practice — not a real PYQ
A temperature difference of 25°C is equal to a difference of
- (a)25 K
- (b)298 K
- (c)248 K
- (d)45 K
Answer(a) 25 K — a difference of 1°C equals a difference of 1 K, so the interval is unchanged.
- practice — not a real PYQ
A body is at 300 K. Its temperature on the Celsius scale is about
- (a)27°C
- (b)300°C
- (c)-27°C
- (d)573°C
Answer(a) 27°C — subtract the offset: 300 − 273 = 27°C.