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The master conversion formula is one of the most important formulas in temperature measurement. Option A (C/5 = F/9) is wrong — using F directly without subtracting 32 is incorrect because the Fahrenheit scale starts at 32 (not 0) for freezing of water. The formula must account for this offset of 32. Option B (C/100 = (F-32)/180 = R/80 = (K-273)/100) is also correct mathematically (this is the unsimplified form) but the simplified standard form used in all competitive exams is option C. Option C (C/5 = (F-32)/9 = R/4 = (K-273)/5) is CORRECT — this is the standard simplified master conversion formula. It is derived from: Celsius has 100 divisions Fahrenheit has 180 divisions Reamur has 80 divisions Kelvin has 100 divisions (273 to 373). Simplified ratios: 100:180:80:100 = 5:9:4:5. Thus: C/5 = (F-32)/9 = R/4 = (K-273)/5. Option D (C = F-32 = R = K-273) is wrong — this would mean 0°C = 32-32=0°F (wrong 0°C=32°F) and 0°C = 0-273 = -273K (wrong 0°C=273K). This formula has no valid basis.
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Heat is a form of energy that transfers between objects or systems due to a temperature difference, moving from a hotter body to a cooler one until thermal equilibrium is reached.
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