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When the atmospheric pressure is low in summer, the professional fish farmers need to add oxygen to the fish pond to prevent the death of fish from hypoxia. Xiao Ming designed an automatic oxygenation system. He modified the mercury barometer in the laboratory. A copper wire is sealed at the left top of the barometer, and a copper wire is fixed at the right opening, as shown in the figure. The mercury surface on the left of the barometer is above the vacuum. When the left mercury surface drops, the right mercury surface will rise. If the external atmospheric pressure is lower than the pressure generated by the 74cm high mercury column, the mercury column will connect the copper wires on both sides, so that the control circuit of the electromagnetic relay will form a path, and the electromagnet will absorb the armature. When the working circuit is connected, the oxygenation pump (AC motor) works automatically. (1) The copper conductor on the right side of the barometer shall be extended vertically downward to the right center of ______cm. Please draw it in the figure at the same time. (2) Please connect the circuit directly in the drawing according to the requirements.
It can be seen from the drawing that when the left silver surface drops by 1cm and the right silver surface rises by 1cm, the height difference between the two sides of the silver surface is 74cm, so the end point of the right copper conductor should be at 11cm of the right scale (in the drawing, the height difference between the silver surface is 76cm, and the right silver surface is already at 10cm of the scale. As long as the right silver surface rises by 1cm, it can...
A bubble is mixed in the mercury barometer and rises above the mercury column, so that the vacuum is no longer above the mercury barometer. When the actual atmospheric pressure is equal to 768mmHg, the reading of the barometer is only 750mmHg. At this time, the distance from the mercury surface in the pipe to the pipe top is 80mm. When the reading of the barometer is 740mmHg, what is the actual atmospheric pressure?
Answer: The actual atmospheric pressure is 756mmHg
Let the cross-sectional area of the mercury tube be S
Select the liquid level at the 0 scale line of the mercury tube as the reference liquid level. Since the liquid level is still, it indicates the force balance:
Pa*S=P1*S+P2*S,(1)
Where Pa is the external atmospheric pressure, P1 is the pressure of the mercury column to the liquid level, and P2 is the pressure of the air bubble at the liquid level
When the external atmospheric pressure is 768mmHg, P1=750mmHg
Get: P2=768-750=18mmHg
Since P*V=constant is obtain according to that Crabtree equation,
So P2*S*H1=P2'*S*H2
Where, H1=80mm, H2=90mm
So P2'=16 mm Hg
Then according to equation (1)
Calculate the external atmospheric pressure Pa' as
Pa'*S=P1'*S+P2'*S
P1'=740mmHg P2'=16 mm Hg
So Pa'=756 mmHg
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