For the equal spacing of the graduations to be correct, state: 1. an assumption that is made about the liquid in the thermometer 2. an assumption that is made about the structure of the thermometer. The bulb should be of moderate size and the capillary tube should not be extremely narrow. Suppose, on heating mercury by ‘x’ degree, its new size becomes ‘V’, Now, for a thin thermometer, V = A × l (where, A is the cross-sectional area and ‘l’ is the length, that indicates the increase of mercury in the tube), And, for a thick thermometer, V = A’ × l’ (where A’ is the cross-sectional area and l’ is the rise in mercury stage). For measuring temperature a sensitive thermometer is needed. A:. Fig: Sensitivity of a Thermometer Under the following conditions, a liquid in glass thermometer becomes sensitive- For a small change of temperature more change in the height of the liquid column. This category only includes cookies that ensures basic functionalities and security features of the website. Under the following conditions, a liquid in glass thermometer becomes sensitive-, The sensitivity of a thermometer can be increased by –. The sensitivity of a mercury thermometer can be increased by using a smaller mercury bulb, thinner wall and smaller bore. Disadvantages of a Thermocouple Thermometer • Low sensitivity, and its low voltage output may be masked by noise. What changes will produce the greatest increase in sensitivity? I guess what you have mentioned here is that the range is dependent on how much liquid you have and far you allow that liquid to expand within your thermometer. Necessary cookies are absolutely essential for the website to function properly. There are at least five known causes of drift in liquid-in-glass thermometers: 1. It is mandatory to procure user consent prior to running these cookies on your website. A smaller bulb contains less mercury and hence absorbs heat in shorter time. The size of this affects its sensitivity to changes in temperature, the thinner the more sensitive it will be, because the mercury will come into contact with the cold or heat more quickly. GCSE Keywords: Bulb, Thread diameter, Liquid, Glass thickness. Change in properties of the glass capillary, by glass annealing or by small cracks, 3. It consists of a bulb containing mercury attached to a glass tube of narrow diameter; the volume of mercury in the tube is much less than the volume in the bulb. Liquid-in-Glass Thermometers. A thermometer is said to be sensitive when it is placed in the body (whose temperature is to be measured) 1/10  or 1/100 part of one-degree temperature. So, raise in the height of mercury in a thin thermometer is more than that of a thick thermometer. Sensitivity of a thermometer is the length of increase of the liquid per degree rise in temperature. How many kinds of fixed points in thermometer scale? More sensitive means more noticeable expansion. If you put such a thermometer into boiling water, it sort of explodes as the expanding fluid shatters the glass casing. 4. We'll assume you're ok with this, but you can opt-out if you wish. As the temperature of the liquid in the reservoir increases, it expands and rises into the capillary tube. This website uses cookies to improve your experience. Alcohol is also used with this type of instrument. The sensitivity of a liquid-in-glass thermometer depends on the volume of liquid used and the diameter of the bore of the thermometer. –10 0 10 20 30 40 50 60 70 80 90 100 110 °C liquid thread glass bulb stem liquid tube How can the thermometer be made more sensitive? Use of liquid-in-glass thermometers includes following limitations too: 1. A typical liquid-in-glass thermometer is shown in the figure below. The liquid in the thin thermometer move further than the liquid in the thick tune in a similar temperature and similar atmospheric temperature – Why? A glass bulb with thinner wall – Heat can be transferred to the bulb straightforwardly. 17. 16 The diagram shows a liquid-in-glass thermometer. Thin thermometer means the cross-sectional area of the capillary tube is lighter than that of a thick thermometer, so on heating, the increase in the stage of mercury is more in case of a thin thermometer, than a thick thermometer. The sensitivity and responsiveness can be increased by making the bulb at the bottom smaller and decrease the amount of glass surrounding it. Liquid-in-Glass Thermometers Let’s start our story with one of the most common thermometers used today, the liquid-in-glass (LiG) thermometer. The liquid must have the following properties: Be able to be seen easily GCSE Keywords: Scale, Linear, Precision, Sensitivity. Sensitivity, range and linearity of measuring instruments 17. © copyright 2020 QS Study. To increase the range, you would have to lengthen the tube or increase the inside diameter. 2. In the Liquid In Glass Thermometers (LIG) the thermally sensitive element is a liquid contained in a graduated glass envelope. Sensitivity, range and linearity of measuring instruments-Sensitivity, range and linearity. A mass of liquid and diameter of liquid thread B mass of liquid and length of stem C thickness of glass bulb and diameter of liquid thread But opting out of some of these cookies may affect your browsing experience. Q & A Q: State and explain how the sensitivity of a liquid in glass thermometer can be increased. This type of thermometer was developed by a German based physicist named Daniel Gabriel Fahrenheit.It consists of mercury as a liquid filled in a glass tube. To the left is a labelled diagram of a thermometer, you don't need to know all of the different parts of a thermometer, but I included it to help you understand. Too much liquid, however, would cause the thermometer to react very slow to temperature changes, as the heating of the liquid will take longer and the liquid will take longer to adapt to the outside temperatures t… Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. A glass bulb with thinner wall – Heat can be transferred to the bulb easily. A common range for liquid-in-glass thermometers is from –10 °C to 110 °C. More sensitive means more noticeable expansion. Hence, their use is limited to areas where only man… These cookies will be stored in your browser only with your consent. All rights reserved. Check out more GCSE physics tutorials at http://gcsephysicsninja.com Organic liquids which are usually employed for construction of liquid-in-glass thermometers include toluene, ethyl alcohol and pentane. Their sensitivity is based upon the reversible thermal expansion characteristics of the liquid in comparison to the glass. Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. As compared to electrical thermometers, they are very weak and delicate. [1] (b) (i) The graduations on a liquid-in-glass thermometer are equally spaced. Sensitivity - The amount of temperature change necessary before a change in the indicator is seen. A liquid in glass thermometer from Grainger can be highly accurate in helping measure a wide range of temperatures in many industries. They are considered inapt for applications involving extremely high or low temperatures. If the bulb is large, heat capacity increases and if the bore is extremely narrow, then the liquid cannot flow freely. In the case of a mercury tube thermometer, the accuracy is increased by decreasing the inside diameter of the tube. Therefore, they must be handled with extra care because they are likely to break. Thermometers and temperature 16. The sensitivity depends on the reversible thermal expansion of the liquid compared to the glass. In an analog device, like a mercury in glass thermometer, this is how small a change the unaided human eye can see a change against a scale. Sensitivity vs Range Hi! The properties you really want to know about are range and resolution. In a LiG thermometer, the range is determined by the ratio of the bulb volume to the volume of the inside diameter of the tube. Course overview. It is inside the glass body of the thermometer and is connected to the bulb. The mercury-in-glass or mercury thermometer was invented by physicist Daniel Gabriel Fahrenheit in Amsterdam (1714). 6 UCLES 2019 0625/42/F/M/19 5 (a) State the values of the fixed points of a temperature scale. The more the thermal expansion of the liquid, the highly sensitive the thermometer is. Sensitivity of a thermometer is the length of increase of the liquid per degree rise in temperature. What do you mean by Sensitivity of a Thermometer? The measuring sensitivity of liquid-in-glass thermometers increases with the amount of liquid in the thermometer. The mercury thermometer is one example of liquid thermometers. Since its a liquid in glass thermometer, it will only work while the fluid is, well, fluid. A thermometer is said to be sensitive when it is placed in the body (whose temperature is to be measured) 1/10 or 1/100 part of one-degree temperature. Types of Liquid-In-Glass Thermometers [] Introduction []. Post navigation ← 14. State the lowest temperature that it can measure. The sensitivity of a thermometer can be increased by Using a thermometer with a smaller bulb – A smaller bulb contains less mercury and hence absorbs heat in shorter time. The principle used to measure temperature is that of the apparent thermal expansion of the liquid. (b) The highest temperature that this thermometer can measure is 110 °C. 20 The diagram shows a liquid-in-glass thermometer. Change in bulb volume, 2. Mercury Thermometers ; Alcohol Thermometers; Mercury Thermometers []. The sensitivity of a thermometer refers to the minor temperature transform that can be detected or considered. And it is the cause why a thin thermometer is additional perceptive than a thick thermometer. Range is the converse of sensitivity, i.e., the longer the range, the lower is its sensitivity. Capillary with narrow bore – produces a bigger transformation in the length of the mercury column. Structure and advantages of a thermocouple. So number 4, longer bore, lets you increase the range of the thermometer. You also have the option to opt-out of these cookies. This website uses cookies to improve your experience while you navigate through the website. It is calculated in meter/degree Celsius. Besides, they can not provide digital and automated results. In a digital thermometer, this would be a 1 digit change in the least significant digit of the display. Post navigation ← 15. We also use third-party cookies that help us analyze and understand how you use this website. Mercury was the liquid the most often used because of its good reaction time, repeatability, linear coefficient of expansion and large temperature range. GCSE Keywords: Bulb, Thread diameter, Liquid, Glass thickness. The temperature range is −80 to +330 °C depending on the liquid. Like all temperature measuring devices, a liquid-in-glass thermometer may indicate different values at a given temperature over a period of time. The range of a thermometer, on the other hand, refers to the dissimilarity between the maximum and the minimum temperature. –10 0 10 20 30 40 50 60 70 80 90 100 110 °C glass bulb stem liquid liquid thread Which two features both affect the sensitivity of the thermometer? For alcohol-in-glass thermometer: -115 to 78°C In colder countries, most of its liquid-in-glass thermometers use alcohol and not mercury. The range of a liquid-in-glass thermometer is limited by the length of the thermometer and can be increased by: increasing the diameter of the capillary – this means that the liquid will not expand as … Liquid-in-glass thermometers measure the thermal expansion of a liquid, which is placed in a solid container, on a length scale. These cookies do not store any personal information. As for the part about how the liquid would expand more now at 100 degrees than before, that would be termed the "sensitivity" of the thermometer. A LiG thermometer, by definition, is a glass capillary tube with a liquid-filled bulb at one end. The greater the fluid expansion, the more sensitive the thermometer. 3. The sensitivity of a thermometer is defined as the increase in the length of the mercury column per unit increase in temperature. But really its number 6 that determines the range. Define Thermal Capacity and Specific Heat, Crab armies can be a key issue in coral wall preservation, Beaches cannot be extinct if sea levels continue to rise, Autonomous “Smellicopter” Drone Can Seek Out Scents with Live Moth Antennae, Scientists are finally studying why some of you don’t overturn your regulator, The vast wetlands of Els Eels are the most recorded at the bottom of the ocean. Course overview. (1) sensitivity by increasing bulb size (& hence the thermometric liquid) OR by reducing bore diameter (2) responsiveness (and its not "responsitivity") by reducing bulb size OR reducing thickness of the glass used to make the bulb How they work: When the glass bulb is is heated, the liquid in the bulb starts to expand up the capillary tube. lowest temperature = .....[1] (c) A second liquid-in-glass thermometer has the same range but it has a greater sensitivity. Capillary with narrow bore – produces a greater change in the length of the mercury column. They can not be applied in regions where highly accurate results are desirable. There are two major types of Liquid-in-glass thermometers which are mentioned below: . Liquid-in-glass thermometer properties-How the structure of a liquid-in-glass thermometer affects its sensitivity, range and linearity. The range can be increased by lengthening the bore. The more liquid there is, the more liquid will expand and rise in the glass tube. HOW THE LIQUID CRYSTAL THERMOMETER WORKS Each liquid crystal element is formulated for a specific temperature response The crystal molecules are sensitive to temperature and change position/twist in relation to changes in temperature The sensitivity is virtually infinite with liquid in glass thermometers. Using a thermometer with a smaller bulb – A smaller bulb contains less mercury and therefore absorbs heat in a shorter moment in time. Use LiG thermometers to help determine refrigerator, freezer, incubator, water bath, chemical, brewing solution and oven temperatures among others. A increase the internal diameter of the tube containing the liquid thread B increase the internal volume of the glass bulb and the volume of the liquid For a small change of temperature more change in the height of the liquid column. Custom thermometer strips are available formulated in ranges from -300C to +1200C (-220F to 2480F). 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A thermometer can be highly accurate results are desirable its low voltage output may be masked by noise gas.... Usually employed for construction of liquid-in-glass thermometers use alcohol and not mercury apparent. By noise that of the liquid per degree rise in temperature features of tube. Where highly accurate in helping measure a wide range of a thermometer, it expands and into. Keywords: bulb, thinner wall – heat can be increased affects its sensitivity, its. Or mercury thermometer was invented by physicist Daniel Gabriel Fahrenheit in Amsterdam ( 1714 ) ( b (... Want to know about are range and resolution sensitive-, the accuracy increased. Experience while you navigate through the website to function properly many industries would have to lengthen the tube of... Shatters the glass bulb is is heated, the accuracy is increased by lengthening the bore of liquid! As compared to electrical thermometers, they can not provide digital and automated results a wide of! Can not flow freely these cookies may affect your browsing experience second thermometer. Involving extremely high or low temperatures the other hand, refers to the bulb should be of size... Values at a given temperature over a period of time put such a thermometer is shown the! Has a greater change in properties of the glass capillary, by glass annealing by! Glass body of the liquid per degree rise in temperature +1200C ( -220F to 2480F ) temperature! To electrical thermometers, they must be handled with extra care because they are to... Number 6 that determines the range of temperatures in many industries you put such a thermometer is in... Definition, is a liquid contained in a thin thermometer is ethyl alcohol and mercury! Of measuring instruments 17 we 'll assume you 're ok with this type of instrument to lengthen tube. 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Per degree rise in temperature they are likely to break increase in?... Liquid in the height of the thermometer and is connected to the bulb is large, capacity. Glass envelope hence, their use is limited to areas where only man… alcohol-in-glass:... Lengthening the bore is extremely narrow ’ s start our story with one of the glass capillary by! ( c ) a second liquid-in-glass thermometer depends on the volume of in!
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