物理問題有關heat

The most important process that needs to take into account in the two situations you described is the exchange of heat energy with the environment. Such energy exchange cannot be ignored in the real situation, especially at high temperature.

The temperature of the brass block does not rise further because the heat given to the block by the flame just balances the heat loss to the surroundings. Generally speaking, the rate of heat loss is more or less proportional to the difference in temperature of the heated object to that of the surroundings (this is Newtons Law of Cooling). The higher the temperature of the brass block, the rate of heat loss would increase. When a certain temperature is reached such that the heat gained by the block from the flame equals to the heat loss from the block to the environment, a dynamic equilibrium is reached and the temperature of the block would not rise any further.

For similar reason, the kettle only serves as a heat conduction medium, providing a [path] for heat to flow from the fire to the water. The inner side of the kettle in contact with the water could be at a temperature lower than the outer side in contact with the fire. Thus, the temperature of water in the kettle could be lower than the temperature of the fire.

If the temperature of water remains at 50 degrees Celsius and does not rise further, this indicates that the fire is not strong enough, such that the heat energy supplied to the water is all lost to the surroundings, leaving no excess heat energy to raise the water temperature further.

火燒鐵, 鐵之所以會上升溫度, 係因為火既溫度比鐵高, 溫度唔同就會有能量由高流去低, 當鐵既溫度同火既溫度一樣既時候, 能量都唔會再由火傳去鐵, 咁鐵既溫度點會再升呢? 所以最後火同鐵既溫度咪一樣囉