Difficulty: Easy
Correct Answer: °R = °F + 273
Explanation:
Introduction / Context:Accurate temperature conversions are essential across thermodynamics, heat transfer, and instrumentation. Rømer, Rankine, Celsius, Fahrenheit, and Kelvin scales often appear in legacy data or vendor specifications; choosing the correct formula avoids significant calculation errors.
Given Data / Assumptions:
Concept / Approach:Check each formula against the standard relations. Remember that offsets differ between pairs: Rankine and Fahrenheit share degree size but different zero; Kelvin and Celsius share offset at zero. Differences (not absolute values) convert without offsets, but magnitudes scale by 9/5 between °F and °C/K.
Step-by-Step Evaluation:
(a) Claimed °R = °F + 273 is wrong; correct is °R = °F + 459.67.(b) Differences: 1 K = 1 °C = 1.8 °F → correct for temperature intervals.(c) °C = (°F − 32) × 5/9 ≈ (°F − 32) × 0.555 → correct.(d) °F = 1.8 × (°C + 17.778) is algebraically the same as °F = 1.8 °C + 32 → correct.Verification / Alternative check:Test with °C = 0: (d) gives °F = 1.8 × 17.778 ≈ 32, as expected. For (a), if °F = 0, formula would give °R = 273, but the actual Rankine at 0 °F is 459.67 °R.
Why Other Options Are Wrong or Right:
Common Pitfalls:Confusing absolute temperatures with temperature differences; mixing the Kelvin and Rankine offsets; rounding offsets too aggressively.
Final Answer:°R = °F + 273
Discussion & Comments