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 answer
Explanation
The correct answer is B, 30°C. One kelvin and one degree Celsius are the same size, so a rise of 30 K is also a rise of 30°C.
The Kelvin and Celsius scales differ only in their starting point: T(K) = t(°C) + 273 (more exactly 273.15). When we take a difference between two temperatures, the 273 cancels out. Here 310 K is about 37°C, close to normal body temperature, and 340 K is about 67°C. The rise is 340 − 310 = 30 K, which equals 67 − 37 = 30°C.
A is wrong: 20°C does not match the 30-unit gap between the two readings.
C is wrong: 37°C is the starting temperature itself (310 K), not the increase.
D is wrong: 67°C is the final temperature (340 K), not the increase.
Exam tip: to convert a temperature subtract 273, but a temperature change is the same number in kelvin and in degrees Celsius.
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