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Celsius and Fahrenheit are the two commonly used scales used to measure temperature. The unit of temperature in the Celsius scale will be expressed in degrees Celsius (or degrees centigrade). The temperature will be stated in degrees Fahrenheit on the Fahrenheit scale.
Celsius Scale
The Celsius scale was designed by Andre Celcius in 1742.
- It defines the ice point temperature as 0 ℃ and the steam point temperature as 100 ℃.
- The space between 0 ℃ and 100 ℃ is divided into 100 equal parts.
Fahrenheit Scale
The Fahrenheit scale was designed by Fahrenheit in 1724.
- It defines the ice point temperature as 32 ℉ and the steam point temperature as 212 ℉.
- The space between 32 ℉ and 212 ℉ is divided into 180 equal parts.
The conversion of the Fahrenheit scale to the Celcius scale is given by
TC = 5/9 (TF – 32)
The conversion of the Celcius scale to the Fahrenheit scale is given by
TF = (9/5)TC + 32
Very Short Answers Questions [1 Mark Questions]
Ques. What is the average human body temperature in Fahrenheit and Celcius?
Ans. The average temperature of the human body is 98.6 ℉ or 37 ℃.
Ques. What are the units to measure the temperature?
Ans. The SI unit of temperature is Kelvin (K). Commonly used units of temperature are Celcius (℃) and Fahrenheit (℉).
Ques. What is the melting point of ice in Celsius?
Ans. The melting point of ice, also known as ice point is zero degrees Celsius (0 ℃).
Ques. Who invented the Fahrenheit system?
Ans. The Fahrenheit system to measure temperature was invented by Daniel Gabriel Fahrenheit in 1724.
Short Answers Questions [2 Marks Questions]
Ques. What is temperature?
Ans. The temperature of a substance is a physical quantity that measures the degree of hotness and coldness of the substance. It determines whether the heat energy flows from one body to another body or not.
Ques. Define Thermometry.
Ans. A branch of science that deals with the measurement of the temperature of a substance is known as thermometry.
The property of a substance that changes with the change in temperature is called its thermometric property.
Ques. At what temperature K is equal to F?
Ans. Let at temperature T the Kelvin scale temperature (TK) becomes equal to the Fahrenheit scale temperature (TF).
The formula for the conversion of the Kelvin scale to the Fahrenheit scale is given by
TF = (9/5)TK – 459.67
On substituting TF = TK = x, we get
x = (9/5)x – 459.67
⇒ x = 574.25
Ques. Define the Absolute scale of temperature.
Ans. The scale of temperature whose zero coincides with - 273.15 ℃ is known as the Absolute scale or Kelvin scale.
The zero of the absolute scale of temperature is denoted by 0 K and is known as absolute zero.
Read More:
| Related Concepts | ||
|---|---|---|
| Thermal Stress | Working of Boiler | Thermal Energy Formula |
| Impact of Temperature | Latent Heat of Water | Heat of Vapourization |
| Calorimeter Formula | Celsius to Kelvin | Heat Rate |
Long Answers Questions [3 Marks Questions]
Ques. Write the differences between Celcius and Fahrenheit scales.
Ans. The followings are the differences between Celcius and Fahrenheit scales
| Celcius scale | Fahrenheit scale |
|---|---|
| This scale was designed by Andre Celcius in 1742. | This scale was designed by Fahrenheit in 1724. |
| It defines the ice point temperature as 0 ℃ and the steam point temperature as 100 ℃. | It defines the ice point temperature as 32 ℉ and the steam point temperature as 212 ℉. |
| The space between 0 ℃ and 100 ℃ is divided into 100 equal parts. | The space between 32 ℉ and 212 ℉ is divided into 180 equal parts. |
| The conversion of the Fahrenheit scale to the Celcius scale is given by TC = 5/9 (TF - 32) | The conversion of the Celcius scale to the Fahrenheit scale is given by TF = (9/5)TC + 32 |
Ques. Convert 40 ℃ to the Fahrenheit scale.
Ans. The conversion of the Celcius scale to the Fahrenheit scale is given by
TF = (9/5)TC + 32
Where
- TC is the temperature in the Celcius scale
- TF is the temperature in the Fahrenheit scale
Given TC = 40 ℃, therefore
TF = (9/5) x 40 + 32
⇒ TF = 104 ℉
Ques. What would the value of Fahrenheit be at 574.59 K?
Ans. The conversion of the Kelvin scale to the Fahrenheit scale is given by
TF = (9/5)TK – 459.67
Where
- TK is the temperature in the Kelvin scale
- TF is the temperature in the Fahrenheit scale
Given TK = 574.59 K, therefore
TF = (9/5) x 574.59 – 459.67
⇒ TF = 574.592 ℉
Very Long Answers Questions [5 Marks Questions]
Ques. The triple points of neon and carbon dioxide are 24.57 K and 216.55 K respectively. Express the temperatures on the Celcius and Fahrenheit scales.
Ans. For neon,
The triple point of neon in the Kelvin scale, TK = 24.57 K
The conversion of the Kelvin scale into the Celcius scale is given by
TC = TK - 273.15
Where
- TC is the temperature in Celcius scale
- TK is the temperature Kelvin scale
Therefore
TC = 24.57- 273.15 = - 248.58 ℃
The conversion of the Kelvin scale into the Fahrenheit scale is given by
TF = (9/5 TK) – 459.67
Where TF is the temperature Fahrenheit scale
Therefore
TF = (9/5 x 24.57) – 459.67 = - 415.44 ℉
For carbon dioxide,
The triple point of neon in the Kelvin scale, TK = 216.55 K
The conversion of the Kelvin scale into the Celcius scale is given by
TC = TK – 273.15
Therefore
TC = 216.55 – 273.15 = - 56.6 ℃
The conversion of the Kelvin scale into the Fahrenheit scale is given by
TF = (9/5 TK) - 459.67
Therefore
TF = (9/5 x 216.55) - 459.67 = - 69.88 ℉
Ques. A thermometer has the wrong calibration. It reads the melting point of ice as -10 ℃. It reads 60 ℃ in place of 50 ℃. Calculate the temperature of the boiling point of water on this scale.
Ans. Let T1 and T2 be the melting point and boiling point of the wrong calibrated scale and it is divided into n equal parts.
Then we can write
(Boiling point in ℃ - melting point in ℃) / 100 = (T2 - T1) / n
⇒ (100 - 0)/100 = T2 - (-10) / n
⇒ n = T2 + 10
⇒ T2 = n - 10 …(i)
Also,
(Temperature in ℃ - melting point in ℃) / 100 = (Temperature in the wrong scale - melting point in new scale) / n
⇒ (50 - 0)/100 = (60 - T1) / n
⇒ 1 / 2 = 60 - (-10) / n
⇒ n = 140
Substituting the value of n in equation (i), we get
T2 = 140 - 10 = 130 ℃
Ques. The triple point of water is 273.16 K. Express the temperature on the Celcius and Fahrenheit scales.
Ans. Given, the triple point of water in the Kelvin scale, TK = 273.16 K
The conversion of the Kelvin scale into the Celcius scale is given by
TC = TK - 273.15
Where
- TC is the temperature in Celcius scale
- TK is the temperature Kelvin scale
Therefore
TC = 273.16 - 273.15 = 0.01 ℃
The conversion of the Kelvin scale into the Fahrenheit scale is given by
TF = (9/5 TK) - 459.67
Where TF is the temperature Fahrenheit scale
Therefore
TF = (9/5 x 273.16) - 459.67 = 32.018 ℉
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