A, assuming that the mercury column does not move when the ambient temperature changes, the volume changes of the two parts of gas are equal, which is obtained by Charlie's theorem:
P2P 1=T2T 1
From mathematical knowledge: P2? P 1=T2？ T 1T 1
That is △PP 1=△TT 1.
Get △P=△TT 1P 1?
According to the title, in the initial state, the temperatures of the two parts of gas are equal, and the pressure in the lower part of gas is greater than that in the upper part of gas. When the ambient temperature changes and △T remains unchanged, the pressure change in the lower part of the gas is greater than that in the upper part of the gas, and the mercury column moves up, resulting in the volume of the lower part of the gas being greater than that of the upper part of the gas. So, A is wrong.
B, keep balance, the pressure of the lower gas = the pressure of the upper gas+the pressure generated by the mercury column, and the inclination angle of the glass tube remains unchanged, so the pressure generated by the mercury column remains unchanged, that is, the difference between the upper and lower pressures remains unchanged, so the change of the upper and lower pressures is equal, so B is correct.
C, if the upper gas volume becomes larger and the mercury column moves down, assuming that the mercury column is stationary, it can be seen from the analysis of item A that |△P is downward |
D, it can be seen from the above that D is wrong. So, d is wrong.
So choose BC