Table of Contents
Why alcohol is not used in barometer?
Alcohol is not used in barometer because: It cannot measure the high temperatures because of its low boiling point. It makes the wall wet. It is colorless and thus dye must be added to it so as to make it visible.
What happens if the vacuum at the top of a barometer is removed?
Barometer height of mercury column is the balance between pressure on mercury dish in which it stands and the height of mercury column. As vacuum goes up, or air is successively removed from chamber, the level of mercury gradually goes down.
What does the vacuum do in a barometer?
A safer way to fill a barometer is to use a vacuum pump to create a vacuum at the top of the barometer. This draws the mercury up into the tube from the dish at the bottom. Continuing to draw a vacuum does not change the level of the mercury inside the tube. Again, the pressure is 731 millimeters of mercury.
Can we use alcohol instead of mercury?
Explanation: Alcohol thermometers are used rather than mercury thermometers in very cold regions because alcohol has a lower freezing point than mercury. Pure ethanol freezes at -115 degrees C, while mercury freezes at -38 degrees C.
Why is mercury used in a barometer instead of water?
Mercury is commonly used in barometers because its high density means the height of the column can be a reasonable size to measure atmospheric pressure. This is because mercury is 13.6 times more dense than water.
Why is there vacuum above the level of mercury in mercury barometer?
The height of the mercury column varies with atmospheric pressure and can be used to calculate the atmospheric pressure. When the tube filled with mercury is upended into the cistern, there is a fall in the mercury level which leads to the creation of a vacuum space near the top of the tube.
Why is mercury preferred over alcohol?
It is more durable than alcohol thermometer because mercury does not evaporate easily. It is smaller in size as compared to alcohol one. Mercury does not wet the wall of the thermometer, which means that results can be highly accurate.
Why is the top of a barometer filled with nothing?
The top of the barometer is filled with nothing (vacuum) because the mercury must have the space to expand and contract without any other force affecting it; a gas or liquid in the top would have its own pressure against the mercury and give inaccurate readings.
How does a mercury barometer work?
A mercury barometer works by stabilizing the level of mercury in the sealed glass tube with the atmospheric pressure on the open mercury chamber.
How does atmospheric pressure affect the accuracy of a barometer?
High atmospheric pressure pushes the mercury up; low atmospheric pressure allows the mercury to drop. The barometer markings are also adjusted for temperature, as this affects the mercury’s density and also its level in the barometer.
How does the pressure inside a mercury column depend on Mercury?
In such a case the wall of the glass tube exerts downward forces on the mercury inside the tube such that the pressure exerted on the surface of mercury outside the tube is equal to the pressure (due to the column of mercury and the tube) inside the mercury column at the same horizontal level as the mercury surface outside the tube.