Physics unit 2

A small experimental chamber is described by C dT/dt = P − K(T−Ta), where T is its uniform temperature, Ta = 20 °C is ambient temperature, C is total heat capacity in J/K, K is thermal conductance in W/K, and P is electrical heating power in W. Both C and K are constant in each run. With P = 60 W, the temperature settles at 50 °C. With the heater then switched off, readings at 0, 4, 8 and 12 minutes are 50, 35, 27.5 and 23.75 °C. A modification adds material of negligible heat capacity that reduces K by half. A separate modification adds thermal ballast that doubles C without changing K. The model is exact for these conditions.