- #1
rtareen
- 162
- 32
- TL;DR Summary
- A mercury barometer is used to measure the pressure of the atmosphere, we determine the pressure by observing the height of the mercury in a tube.
The figure shows two mercury barometers.
1. My first question is why specifically does it have mercury? Is the mercury a gas or a liquid? Why can we not just use water? Does the pressure of the liquid have to be less than that of the atmosphere for this to work?
2. The book says for a given atmospheric pressure, the height h does not depend on the cross sectional area of the vertical tube. But doesn't the height also depend on the volume of mercury? If you have less mercury its volume will fill out less of the tube and h will be smaller.
3. How do you actually get this to work? Do you fill the tube completely then invert it into the dish? What if it overflows? Is the tube supposed to float on the mercury below it?