# Homework Help: Measuring the thermal diffusivity.

1. Dec 13, 2009

### Tsportmat

1. The problem statement, all variables and given/known data

Evening everybody. I am attempting to devise an experiment in order to measure the thermal diffusivity of ice and water.

Imagine 3 brass plates, with water held between them, in approximately a 1mm gap (dx) by surface tension.
The 3 plates have thermocouples between them in order to tell the difference in temperature between them. The part I am miffed about is how to obtain the diffusivity from this measurement.

I have been given this equation to link them, but I am struggling to find where it came from and the significance if the d2T/dx2

d2T/dx2=T1-2T2/dx2+T3

2. Relevant equations

dQ/dT=-D dH/dx

3. The attempt at a solution

This is not really appropriate, as the above is an experiment plan which I have devised, I just need the final link! I apologise for not using the exact format, but any ideas or leads for me to follow up would be greatly appreciated, I've come to a dead end.