How Do I Determine the Thermal Conductivity of Glass from My Graph?

[chickens]

Hi there,...this isn't homework..its more to my practical...anyways...from the attachment given..that is the first page of my practical guide...the problem is...on the procedure part...it asked me to plot a graph of lg temp againts t ...if i do so...how do i get the thermal conductivity of glass as the initial temp is 20 C ?!?...so weird...because i don't get lg 20 as interception from the graph...btw..if i simply assume the gradient of graph plotted is kt/Brx ...then my thermal conductivity of glass is 0.2++...i don't think that's right :(...help me anyone..please

http://server2.uploadit.org/files/chickens-exp11.jpg

 

[Gamma]

First of all

thermal conductivity of glass is 0.2++...

What is the unit. IT all depends on the units.

 

[FredGarvin]

I think you need to look at the slope value again. It should be k/Brx since t is your independent variable and k,b,r and x are all constants. Also, pay heed to Gamma. Units will be your downfall if you are not careful.

 

[chickens]

oh..the units are all in W m^(-1) K^(-1)