Identify the incorrect temperature conversion relation:\nChoose the option that is wrong (others are correct reformulations).

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:

  • Kelvin–Celsius: K = °C + 273.15 (≈ 273 for quick estimates).
  • Rankine–Fahrenheit: °R = °F + 459.67.
  • Linear scale relations: °F = (9/5)°C + 32 and °C = (5/9)(°F − 32).
  • Temperature differences: ΔK = Δ°C = (9/5)Δ°F.


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:

  • (a) Wrong due to incorrect zero offset.
  • (b)–(d) are correct relations for differences or equivalent algebraic forms.


Common Pitfalls:
Confusing absolute temperatures with temperature differences; mixing the Kelvin and Rankine offsets; rounding offsets too aggressively.


Final Answer:
°R = °F + 273

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