Dear all, suppose that a mercury thermometer is placed in a vacuumed isolated space without any energy and work interaction with the environment. obviously, the level of mercury is somewhere in the thermometer. what is this temperature?
My guess would be the initial termperature from the thermometer itself. The thermometer does not appear out of thin air, so needs to be inserted with pre-conditions of its own. It will have no exchange with its (vacuum) environment, except for some (tiny) radiation heat loss.The indicated temperature will be the one at point of introduction.
I mean that the heat radiation equilibrium determines the shown temperature. There is an input radiation from the surrounding, and the thermometer itself is a source of radiation towards the surrounding. Initially, before the system reaches equilibrium, the thermometer changes its temperature and after a while it comes to an equilibrium.
Majid,
>without any energy and work interaction with the environment
So, the thermometer is not allowed to radiate or absorb heat?
Okay.
In that case the level of the mercury in the thermometer does not change.
In the case of a thermometer in vacuum it would lose heat by radiation until it reached the temperature of the external environment.