What is the thermal conductivity of He at 1 atm and 0°C? The experimental value at 0°C and 1 atm is 1.4 x 10^-3 J/cm K s and d = 2.2 ?Å.

A semiconductor material has a conductivity of 0.0124 W/cm-K. It has the shape of a rectangular bar with cross sectional area of 1 cm2and length of 3 cm. One end is maintained at 300 °C and the other end at 100 °C. The bar carries a current of 50 A and has resistivity of 1.5x10-3ohm-cm. Assuming the longitudinal surface is insulated, calculated the midpoint temperature in the bar.

rド-1 rf-1 Lk(rc-1)] 1 1. Derive the formula of thermal efficiency e =

3- Derive the rule-of-mixtures equation (a₂ = a{V₁ + amVm) for the coefficient of thermal expansion α₂