During the heat conduction lab experiment students were asked, among other things, to measure the thermal...

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During the heat conduction lab experiment students were asked, among other things, to measure the thermal conductivity of two sample metal rods. Electrical heat was supplied at one end of the rod and heat is extracted from the other end using a running cold water. The axial temperature along the rod including the sample was measured using thermocouple probes mounted in the rod material. Power was supplied to the electrical heater using a variable AC transformer and students have access to the maximum power supply as well as the power percentage when the steady state is reached. Typical data obtained by a group of students of your class are provided below I = 210 mA U 230 V Sample and Rod Diameter D-25mm Temperatures are in "C %P: Power supply percentage The bold temperatures are the temperatures located on the sample material Position mm 0 T1 Set Temperature 70 100 110 20 40 T2 T3 GO T4 52.7 50.6 45.7 66 58.7 80 TS 100 T6 55.8 42.8 40.2 74.9 70 54.1 50.2 90.5 83.9 78.4 67.4 61.7 56.9 120 T7 35.1 42.5 46.4 140 T8 160 T9 32.4 29.2 38.5 34.1 41.7 36.5 %P 33.7 65.7 100 Questions 1) Why it is important the take the reading of the Power supply before the steady state can be reached? 2) Give a physical explanation why the temperature is dropping sharply at the edge of the sample (from T3 to T4) and from (T6 to T7) 3) Evaluate the conductivity of the sample for the three temperature experiments 4) From your own experience give an order of magnitude of the inaccuracy on the Power supply Percentage and find out how it affects the accuracy of the thermal conductivity. 5) Assuming a linear variation of the conductivity with the temperature A(T) (T₁)(1+a (T-To)) find the experimental value of a. During the heat conduction lab experiment students were asked, among other things, to measure the thermal conductivity of two sample metal rods. Electrical heat was supplied at one end of the rod and heat is extracted from the other end using a running cold water. The axial temperature along the rod including the sample was measured using thermocouple probes mounted in the rod material. Power was supplied to the electrical heater using a variable AC transformer and students have access to the maximum power supply as well as the power percentage when the steady state is reached. Typical data obtained by a group of students of your class are provided below I = 210 mA U 230 V Sample and Rod Diameter D-25mm Temperatures are in "C %P: Power supply percentage The bold temperatures are the temperatures located on the sample material Position mm 0 T1 Set Temperature 70 100 110 20 40 T2 T3 GO T4 52.7 50.6 45.7 66 58.7 80 TS 100 T6 55.8 42.8 40.2 74.9 70 54.1 50.2 90.5 83.9 78.4 67.4 61.7 56.9 120 T7 35.1 42.5 46.4 140 T8 160 T9 32.4 29.2 38.5 34.1 41.7 36.5 %P 33.7 65.7 100 Questions 1) Why it is important the take the reading of the Power supply before the steady state can be reached? 2) Give a physical explanation why the temperature is dropping sharply at the edge of the sample (from T3 to T4) and from (T6 to T7) 3) Evaluate the conductivity of the sample for the three temperature experiments 4) From your own experience give an order of magnitude of the inaccuracy on the Power supply Percentage and find out how it affects the accuracy of the thermal conductivity. 5) Assuming a linear variation of the conductivity with the temperature A(T) (T₁)(1+a (T-To)) find the experimental value of a.