Create an Excel worksheet that will convert a temperature difference of 22 Celsius degrees to Fahrenheit degrees. If we were to carry out this conversion by hand using a unit equivalence factor, as described in Ex. 10.1, we would write
Thus, we multiply the given temperature difference by 1.8 to obtain the desired result, which is 39.6 F°. The corresponding Excel worksheet is shown in Fig. 10.5. Notice the value 22, which appears in cell A4. This is the given temperature difference in Celsius degrees. The equivalent temperature difference in Fahrenheit degrees is 39.6, as shown in cell B4. This result was obtained by multiplying the value in cell A4 by 1.8, as seen in the formula bar. Note that the formula shown in cell B4 does not make use of the CONVERT function. (Compare with the method and the result obtained in Example 10.4.)
T he Correct Answer and Explanation is :
Excel Worksheet Description
To convert a temperature difference of 22 Celsius degrees (°C) to Fahrenheit degrees (°F), we use the fact that a temperature difference (not an absolute temperature) is converted by multiplying by 1.8, not by using the full °F = °C × 1.8 + 32 formula (which is for absolute temperatures).
Excel Worksheet Layout
| A | B |
|---|---|
| Celsius (°C) | Fahrenheit (°F) |
| 22 | =A4*1.8 → 39.6 |
- Cell A4: Enter
22(Celsius degrees difference). - Cell B4: Enter formula
=A4*1.8to convert to Fahrenheit degrees.
This setup converts the temperature difference, not the absolute temperature.
Explanation
In thermodynamics and temperature measurement, it’s crucial to distinguish between temperature values and temperature differences. While the formula for converting an absolute temperature from Celsius to Fahrenheit is: °F=°C×95+32,°F = °C \times \frac{9}{5} + 32,
this does not apply when converting temperature differences. A temperature difference or change, such as “a 22°C increase,” converts to Fahrenheit by multiplying only by the ratio of the scales: 95=1.8\frac{9}{5} = 1.8.
This is because the “32” in the absolute conversion formula accounts for the different zero points of the Celsius and Fahrenheit scales. But temperature differences are about scale increments, not fixed points. For every 1°C change, the equivalent Fahrenheit change is 1.8°F. Thus, a 22°C difference becomes: 22°C×1.8=39.6°F.22°C \times 1.8 = 39.6°F.
In Excel, this can be easily modeled without complex functions. In cell A4, we enter the Celsius difference (22), and in B4, we use the formula =A4*1.8. This formula reflects the direct mathematical relationship between Celsius and Fahrenheit differences. It does not use the CONVERT function because that function treats temperature as an absolute measure and adds the 32 offset, which would be incorrect in this context.
By understanding this distinction, users can avoid a common mistake: misapplying the absolute temperature conversion formula to temperature differences, which leads to incorrect results.
