Numerically two thermometers, one in Fahrenheit scale and another in Celsius scale shall read same at
- A.−40°
- B.0°
- C.−273°
- D.100°
Correct answer
Explanation
The correct answer is A, −40°. At this one temperature the Celsius and Fahrenheit scales show the same number.
The two scales are linked by F = (9/5)C + 32. Putting F = C gives C = (9/5)C + 32, so −(4/5)C = 32 and C = −40. Water freezes at 0°C or 32°F and boils at 100°C or 212°F, so 100 Celsius degrees cover the same range as 180 Fahrenheit degrees, which is where the ratio 9/5 comes from. The Fahrenheit scale was devised by Daniel Gabriel Fahrenheit in 1724 and the centigrade scale by Anders Celsius in 1742.
B, 0°, is wrong because 0°C equals 32°F.
C, −273°, is absolute zero on the Celsius scale; in Fahrenheit it is about −459°F.
D, 100°, is wrong because 100°C equals 212°F.
Exam tip: C and F agree at −40; normal body temperature is 37°C = 98.6°F.
Practice Questions
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