A Kelvin thermometer and a Fahrenheit thermometer both give the same reading for a certain sample. What would be the corresponding reading in a Celsius thermometer ?
- A.574
- B.301
- C.273
- D.232
Correct answer
Explanation
The correct answer is B, 301. The Kelvin and Fahrenheit scales read the same at about 574.25, which is about 301 degrees Celsius.
The scales are linked by K = C + 273 and F = (9/5)C + 32. Setting the two readings equal gives C + 273 = 1.8C + 32. So 0.8C = 241, and C = 301.25, about 301 °C. The common Kelvin and Fahrenheit reading is then about 574. A similar well-known result is that the Celsius and Fahrenheit scales agree at minus 40. Such questions test whether you remember the conversion formulas, not the numbers themselves.
A is wrong: 574 is the common Kelvin and Fahrenheit reading, not the Celsius value. C is wrong: 273 is the Kelvin value of 0 °C, the freezing point of water, where the Fahrenheit reading is 32. D is wrong: 232 does not satisfy the equation; at 232 °C the Kelvin reading is about 505 and the Fahrenheit reading about 450.
Exam tip: Celsius equals Fahrenheit at minus 40; Kelvin equals Fahrenheit at about 574, which is about 301 °C.
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