These slides are about lee's disk apparatus

2.  To determine the coefficient of thermal conductivity of
bad conductors by using Lee’s disk method .
 Now here two question arises that what is lee’s disk , and what is
the coefficient of thermal conductivity?
 The answer is not complicated, lee’s disk is an apparatus consist
of metallic cylindrical chamber and a disk.
 While coefficient of thermal conductivity is the quantity of heat
flow in one second through a meter cube of a substance the
opposite faces of which are maintained at a difference of 1 degree
C .

3. 1.Vernier Caliper
2. Lee’s disk apparatus
3.Thermocouples
4. Stop Watch
5.Heating Mantle
6. Insulator to find the value of K .

4.  We have set the apparatus ,then we calculated the
thickness and diameter of insulator with the help of
venire caliper.
 Insert the insulator b/w the disk and the cylindrical vessel.
 Place the thermocouple at T1 and T2 position.
 Then by using heating mantle pass the steam from the
inlet of the vessel, then wait till the temperatures T1 and
T2 reached at steady state, note down the temperatures.
 Then remove the insulator to rise the temperature of disk
almost 15 degrees above the steady state.
 Then allow it to cool down and note the temperature
interval of about 90 seconds .
 Then plot the graph b/w temperature and time.

5. The coefficient of thermal conductivity is denoted by K, which
is equal to
K=-mcd/pi.r^2(t2-t1) *dT/dt ---------(1)
Here
m=mass of the lee’s disk
c= specific heat of iron
d=thickness of the insulator
r= radius of the insulator
t2-t1= steady temperatures of thermocouples
dT/dt= change in temperature/change in time

6. m= 1700 g
c=1.08*10^-1 cal/g.C
d=1.94 cm
r=5.5 cm
t2=79 C
t1=32 C
dT/dt= -0.01C/s
Putting all these values in eq. (1) we get
K= 7.9*10^-4 cal/cm.s.C

7.  In this experiment we concluded that this method is good
for calculating the values of bad conductors .
 If we want to find the coefficient of thermal conductivity
for good conductors this method fails , because of very
little difference between the values of t1 & t2, for
calculating K for good conductors the conductors must be
long enough to get the reasonable difference between t1 &
t2.

8. Any questions about the
experiment