A device, which measures the temperature of a body, is called thermometer. Three temperature scales are used on thermometers: the Celsius, the Fahrenheit, and the Kelvin scale. Most liquid thermometers use mercury or alcohol as thermometric substances. The relationship between the reading on the temperature scales is given by the relation:
Precautions while using thermometer are:
Types of thermometer according to the choice of thermometric liquid
There are two types of thermometers according to the thermometric liquid used. They are:
A mercury thermometer is used to measure the temperature of extreme hot places. Mercury thermometer can measure the temperature of -39^{0} Celsius to 357^{0} Celsius.
Advantages of use of Mercury in thermometer
An alcohol thermometer is used to measure the temperature of extreme cold places. Alcohol thermometer can measure the temperature of - 112^{0} Celsius to 78.3^{0} Celsius.
Advantages of use of Alcohol in thermometer
Calibration of thermometer:
Marking of temperature scale on a thermometer is called calibration. Calibration is done in two ways.
To mark the fixed points
Importance of thermometer:
Alcohol thermometer is preferred for a very cold region because its freezing point of alcohol is - 117°C. So, it can measure the temperature of the very cold region.
Give the reason why the temperature of boiling water can’t be measured using an alcohol thermometer.
Temperature of boiling water can’t be measured using an alcohol thermometer because the temperature of boiling water is at 100°C and that of alcohol is 78°C . So, alcohol boils before water and can’t be measured the boiling point of water.
Constriction presents in a clinical thermometer let the level of mercury increase when the temperature increases but doesn’t let it fall when temperature decreases and it helps to take the correct reading.
A clinical thermometer is jerked before using it to bring the level of mercury in the bulb.
Steel pointers are used in maximum and minimum thermometer to locate the temperature of the region.
Importance of thermometer are as follow:
Thermometer is based on the principle of, ' when a body is heated it expands and when a body is cooled it contracts ’.
I use mercury thermometer to measure the temperature above 80°C because the boiling point of alcohol is 78°C . So, it can’t measure the temperature above 78°C.
Maximum and minimum thermometer is used when maximum and minimum temperature of a region is required.
The advantages of using alcohol instead of mercury in a thermometer are as follows:
The advantage of using alcohol instead of mercury in a thermometer is as follows:
I prefer to use laboratory thermometer to measure the temperature of boiling water.
I prefer to use clinical thermometer to measure the temperature of human body.
They are as follows:
Solution,
\begin{align*} \frac {C - 0}{100} &= \frac {F-32}{180} \\ \text {Here,}\: F =98.6\: \text {Fahrenheit} \\\frac {(C- 0)} {100} &= \frac {(98.6- 32)}{180} \\\text {or,}\:\frac {C}{100} &= \frac {66.6}{180} \\ \text {or,}\: C \times 180 &= 66.6 \times 100\: ( \text {cross multiplication}) \\ \text {or,}\: C &= \frac {666}{18} = 37^o \:\text {Celsius} \\\end{align*}
Solution,
\begin{align*} \frac {C - 0}{100} &= \frac {F-32}{180} \\ \text {Here,}\: F = 0 \: \text {Fahrenheit} \\\frac {(C- 0)} {100} &= \frac {(0- 32)}{180} \\\text {or,}\:\frac {C}{100} &= \frac {-32}{180} \\ \text {or,}\: C \times 180 &= -32\times 100\: ( \text {cross multiplication}) \\ \text {or,}\: C &= \frac {-320}{18} = -17.7^o \:\text {Celsius} \\\end{align*}
Solution,
\begin{align*} \frac {F-32}{180} &= \frac {K-273}{180} \\ \text {Here,}\: F = 200\: \text {Fahrenheit} \\\frac {(200 - 32)} {180} &= \frac {(k- 273)}{100} \\\text {or,}\: K - 273 &= (200 - 32) \times \frac {100}{180} \\ \text {or,} \: k -273 &= (200 - 32) \times \frac {100}{180} \\ k &= 93.3 + 272 = 366.3 \\ \text {Thus,}\: 200\: \text {Farhrenheit} &= 366.6 \: \text {kelvin}\\\end{align*}
\begin{align*} \frac {C - 0}{100} &= \frac {k-273}{100} \\ \text {Here,}\: k = 100\: \text {kelvin} \\\frac {(C- 0)} {100} &= \frac {(100 -273)}{100} \\\text {or,}\: C - 0 &= \frac {-173\times 100}{100} \\ \text {or,}\: C &= -173 \\ \therefore 100\: \text {kelvin} = -173^o \:\text {Celsius} \\\end{align*}
Solution,
\begin{align*} \frac {C - 0}{100} &= \frac {F-32}{180} \\ \text {Here,}\: C = -40\: \text {Fahrenheit} \\\frac {(-40- 0)} {100} &= \frac {(F- 32)}{180} \\\text {or,}\:\frac {-40}{100} &= \frac {F -32}{180} \\ \text {or,}\: -40 \times 180 &= (F-32)\times 100\: ( \text {cross multiplication}) \\ \text {or,}\: F - 32 &= -4 \times 18 \\ \text {or,}\: F &= -40 \\ \therefore \text {The celcius and farenheit degree coincides when the value is}\: -40 \end{align*}
Solution
\begin{align*} \frac {C - 0}{100} &= \frac {K-273}{100} \\ \text {Here,}\: C =200\: \text {Fahrenheit} \\\frac {(200 - 0)} {100} &= \frac {(K-273)}{100} \\\text {or,}\: K - 273 &= 200 \\ \text {or,} \: K &= 200 + 273 \\ \text {or,}\: K &= 473\: \text {kelvin} \\ \therefore 200^o \text {is equal to}\: 473\: \text {kelvin}\\\end{align*}
The S.I. unit for temperature is ______.
kelvin scale
reumer scale
degree celcius
degree farenheit
200 Celsius = ______ Kelvin.
573 Kelvin
373 Kelvin
473 Kelvin
470 Kelvin
-40 Celsius = ______ Farenheit
40 Fahrenheit.
30 Fahrenheit.
400 Fahrenheit.
60 Fahrenheit.
You must login to reply
Pink floyd
the shape of the clinical thermometer is made prismatic why?
Mar 19, 2017
0 Replies
Successfully Posted ...
Please Wait...
principle of thermometer?
Mar 17, 2017
0 Replies
Successfully Posted ...
Please Wait...
udoh, victor samuel
show the diagram for bi-metallic thermometers
Mar 02, 2017
0 Replies
Successfully Posted ...
Please Wait...
Why water is not used in thermometer
Dec 31, 2016
0 Replies
Successfully Posted ...
Please Wait...