Mercury thermometers are rarely used, except in lab thermometers. For human use, they have been replaced by dyed alcohol glass thermometers, or electronic digital thermometers.
Dozens of different types of thermometers are in use today, from mercury to alcohol to bi-metal coil to solid-state.
thermometers today are used to generally see what the temperature in a room is they mainly use mercury to find this out :)
In ordinary bulb thermometers, yes.
The same as they've always done, they measure temperatures.
Digital thermometers have replaced mercury thermometers because mercury is toxic. [Personal commentary: digital thermometers are not accurate and mercury thermometers are so how many people are being harmed by not knowing their temperature versus how many would be harmed by the mercury if accurate thermometers were still used?]
Mercury used to be a popular element for thermometers, but I think it's illegal to make a mercury thermometer because if you break one you have a hazardous situation on your hands. Today thermometers that contain liquid, almost always contain alcohol.
Mercury is used in thermometers barometers and flourescent lightbulbs.
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Thermometers used to have Mercury in them because it is very temperature reactive and a liquid across most temperatures measured in everyday life. However, this practice has been discontinued due to the health risks associated with contact with mercury from broken thermometers; most analog thermometers today use colored ethanol as the measuring fluid.
There are 34 different types of thermometer that range from alcohol thermometers and ear thermometers to medical thermometers and electrical resistance thermometers.
You can and many people do.