A copper pot initially at contains of water also at

PHYSICS · Multi-part · A Level · Physics · Further mechanics and thermal physics · Further mechanics and thermal physics

Problem

1.0\,\text{kg}

copper pot initially at

25\,^{\circ}\text{C}

contains

0.80\,\text{kg}

of water also at

25\,^{\circ}\text{C}

. The pot is placed on a burner that supplies thermal energy at a constant (but unknown) rate. After

5.0\,\text{min}

, the water’s temperature is measured to be

95\,^{\circ}\text{C}

. Assume that no energy is lost to the surroundings and that the temperature of the pot always matches the temperature of the water during heating. The specific heat of copper is

390\,\text{J}\,(\text{kg}\,^{\circ}\text{C})^{-1}

and that of liquid water is

4.18\times10^{3}\,\text{J}\,(\text{kg}\,^{\circ}\text{C})^{-1}

. (a) Calculate the total thermal energy that must be transferred to the pot–water system to reach the final temperature. (b) Determine the average power output of the burner during the

5.0\,\text{min}

heating interval. (c) Discuss one plausible physical factor that could cause the actual power of the burner to be larger than the value computed in part (b), and explain the effect qualitatively.

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