How does a liquid in a glass thermometer work?
Liquid-in-glass thermometers are based on the principle of thermal expansion of substances. A liquid in a glass tube (called a capillary) expands when heated and contracts when cooled. A calibrated scale can then be used to read off the respective temperature that led to the corresponding thermal expansion.
Which liquid is used in liquid in glass thermometer?
Mercury
Mercury, the liquid in the thermometer, is enclosed in a sealed glass bulb that expands into a fine bore present in the stem of the thermometer. A scale is etched along the stem of the thermometer that is used for reading the temperature.
What is the use of the liquid inside the thermometer?
The liquid in glass thermometer, is the most commonly used device to measure temperature and it is inexpensive to make and easy to use. The liquid in glass thermometer has a glass bulb attached to a sealed glass tube (also called the stem or capillary tube).
What are the disadvantages of liquid in glass thermometer?
Disadvantages. Liquid in glass thermometers tend to be fragile and hence easily broken, can only be used where the liquid column is visible, cannot be used for surface temperature measurements, cannot be read from a distance and are unsuitable for high temperature measurements.
Which liquid is not used in liquid-in-glass thermometer?
Water is not able to be used as a thermometer liquid because of its higher freezing point and lower boiling point than the other liquids in general.
Are liquid thermometers accurate?
As is true with most instruments, greater accuracy will likely cost more when measuring temperature. Liquid-in-glass thermometers without mercury are not as accurate, so they should be used when less precision and certainty is acceptable. Because of this, accuracy can fluctuate based on the surface being measured.
Can we use other liquids in thermometer?
Mercury is one of the most familiar materials used in liquid thermometers. Other liquids, such as kerosene or ethanol, may also be used in these types of thermometers. Mercury, for instance, becomes a solid at -38.83 degrees Celsius (-37.89 degrees Fahrenheit).
Why do thermometers use alcohol instead of water?
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. Thermometers rely upon thermal expansion of the liquid in a bulb at the base of a thin glass tube.
Why does liquid rise in a thermometer?
The level of colored liquid rises when the thermometer is placed in hot water. Heat causes the molecules of the liquid to get farther apart. The molecules of the liquid break down into atoms and take up more space.
How does a liquid in glass thermometer work?
A bulb which acts as a container for the functioning liquid where it can easily expand or contract in capacity. A stem, “a glass tube containing a tiny capillary connected to the bulb and enlarged at the bottom into a bulb that is partially filled with a working liquid”.
Which is ASTM specification for liquid in glass thermometer?
ASTM has developed a specification for low-hazard precision LiG thermometers, ASTM E 2251, Specification for Liquid-in-Glass ASTM Thermometers with Low-Hazard Precision Liquids. This standard provides specific details on proper use of these devices, the repeatability of their measurements, and other limitations.
What kind of alcohol is in glass thermometer?
The bulb is typically filled with either mercury or red-coloured alcohol and is free to expand and rise up into the tube when the temperature increases, and to contract and move down the tube when the temperature decreases.
What makes up the stem of a Lig thermometer?
The bulb is carefully designed to contain a calculated volume of liquid, based upon the length and diameter of the capillary (or stem), as well as the thermal expansion coefficient of the liquid. The stem, or capillary, of a LiG thermometer is made of annealed glass.