# Degrees Celcius to Farenheight, Conversion issues

1. Oct 7, 2012

### Nellen2222

Degrees Celcius to Farenheight, Conversion issues !!

1. The problem statement, all variables and given/known data
You work in a materials testing lab ad your boss tells you to increase the temperature of a sample by 41.7 degrees celcius. Theo nly thermometer you can find at your workbench reads in degrees fahrenheit. If the initial temperature of the sample is 68.2 degrees farenheight, what is its temperature in degrees farenheight when the desired temperature increase has been achieved?

2. Relevant equations

F degrees = (1.8*C) + 32

3. The attempt at a solution

Tried changing 41.1 degrees celcius into fareneheight and got 107.06. Added that to the initial degrees and got 175.26 Farenheight. However, the answer is still wrong. (3 sig dig rounded to its actually 175.. not that the answer is correct)

What am i doing wrong?

2. Oct 7, 2012

### Dickfore

Re: Degrees Celcius to Farenheight, Conversion issues !!

Degrees Celsius/Fahrenheit is not the same as Celsius/Fahrenheit degrees. This is a sentence whose meaning is that there is a difference between a given temperature, and a temperature difference. Your equation is actually valid only for given temperatures. For temperature intervals, you need:
$$\begin{array}{l} \frac{t_1}{\mathrm{^{o}F}} = \frac{9}{5} \, \frac{t_1}{\mathrm{^{o}C}} + 32 \\ \frac{t_2}{\mathrm{^{o}F}} = \frac{9}{5} \, \frac{t_2}{\mathrm{^{o}C}} + 32 \end{array}$$
$$\frac{t_2 - t_1}{\mathrm{F^{o}}} = \frac{9}{5} \, \frac{t_2 - t_1}{\mathrm{C^{o}}}$$

Notice the different placement of the "o" symbol. One denotes degrees Celsius/Fahrenheit (current temperature), and the other denotes Celsius/Fahrenheit degrees (temperature interval).

3. Oct 7, 2012

### lewando

Re: Degrees Celcius to Farenheight, Conversion issues !!

A change of 1°F equals a change of 1.8°C.

4. Oct 7, 2012

### CWatters

Re: Degrees Celcius to Farenheight, Conversion issues !!

The equation for converting C to F can't be used to convert ΔC to ΔF directly.

Try converting 68.2F to C, add 41.7C and convert it back.

5. Oct 7, 2012

### Staff: Mentor

Re: Degrees Celcius to Farenheight, Conversion issues !!

If F = 1.8 C + 32, then

ΔF = 1.8 Δ C

What is ΔF if ΔC = 41.1?

6. Oct 7, 2012

### skeptic2

Re: Degrees Celcius to Farenheight, Conversion issues !!

This equation is wrong for converting temperature differences from Celsius to Fahrenheit. Do not add the 32 deg. While Celsius degrees are 1.8 deg. larger than Fahrenheit degrees, the 32 degrees only provide and offset to align the two scales.