## FRANK Solutions for Class 9 Physics Chapter 5 - Heat - Thermometry

Question 1
What do you mean by temperature?
Solution 1
Temperature is the quantity that tells about the thermal state of a body i.e. the degree of hotness or coldness of a body.
Question 2
State three properties of a liquid which make it suitable to be used in a thermometer.
Solution 2
Three properties of a liquid which make it suitable to be used in a thermometer are:
(i) The substance should have high coefficient of expansion so that it is sensitive to the smallest change in temperature
(ii) The substance should have uniform expansion all over its entire volume
(iii) The substance should have minimum specific heat so that it absorbs minimum heat from the body under measurement.

Question 3
State two disadvantages of using mercury as a thermometric liquid.
Solution 3
Two disadvantages of using mercury as a thermometric liquid:
(i) It does not have uniform expansion.
(ii) Mercury is less sensitive than alcohol as its coefficient of expansion is less than alcohol.
Question 4
State three advantages of using mercury in a thermometer liquid.
Solution 4
Three advantages of using mercury as a thermometric liquid:
(i) Mercury is good conductors of heat.
(ii) Mercury have high coefficient of expansion thus is sensitive to the smallest change in temperature.
(iii) Freezing points is very low and boiling point is high.

Question 5
State two disadvantages of using water as a thermometric liquid.
Solution 5
Water is not used as a thermometric liquid because it has low coefficient of expansion so it is less sensitive to temperature changes. Moreover, it is transparent thus making it difficult to read the thermometer and water evaporates with time thus producing error and also the freezing and boiling points are also low.
Question 6
Express 00C in Kelvin.
Solution 6
Temperature in Kelvin To K = Temperature in Celsius To C + 273.
To K = 0oC + 273
To K =273 K.

Question 7
The body temperature of a healthy person is 98.40F. Find the corresponding temperature on the Celsius scale.
Solution 7
Body temperature of a healthy person is 98.4oF.
We know C/100 = (F - 32)/180.
C =5/9(F- 32)
C = 5/9(98.4 - 32)
C = 5/9 X66.4
C =36.88oC
Temperature of body of healthy man is 36.88oC.
Question 8
The temperature of a body rises through 10C. What is the corresponding  rise on absolute scale?
Solution 8
Absolute scale of temperature is Kelvin scale.
Conversion of temperature from Celsius to Kelvin scale is
Temperature in Kelvin To K = Temperature in Celsius To C + 273.
So a rise of temperature of 1oC in Celsius scale is equal to rise of 1oK in Kelvin scale.

Question 9
Name the temperature scale used in SI system.
Solution 9
Kelvin temperature scale is used in SI system.
Question 10
How is the size of a degree defined on the Celsius scale?
Solution 10
In Celsius scale there are two fixed points namely lower fixed point and upper fixed point at 0oC and 100oC respectively. This range is divided into 100 equal divisions and each part gives 1oC.

Question 11
Convert -150C on the Fahrenheit scale.
Solution 11
We know C/100 = (F - 32)/180.
C =5/9(F- 32)
9/5C + 32 =F
F = 9/5C + 32.
Temperature given in Celsius = -15oC.
F = 9/5 X (-15) +32
F = -27 +32
F = 5oF.
Question 12
Name the instrument used for measuring the temperature of a body.
Solution 12
Thermometer is used for measuring the temperature of a body.

Question 13
What is absolute zero on the Celsius Scale?
Solution 13
Absolute zero of temperature is 0oK.
Temperature in Kelvin To K = Temperature in Celsius To C + 273.
0oK = To C +273.
To C = -273oC.
Absolute zero of temperature on Celsius scale is -273oC.
Question 14
The temp. of two bodies differ by 10C. What is the difference on Fahrenheit scale of temperature?
Solution 14
Difference of temperature of two bodies in Celsius scale = 1oC.
We know C/100 = (F - 32)/180.
C =5/9(F- 32)
9/5C + 32 =F
F = 9/5C + 32.
So, difference of 1o in Celsius scale is equal to the difference of 9/5o in Fahrenheit scale.
Thus, Difference of 1oC of temperature of two bodies in Celsius scale is equal to difference of 1.8o in Fahrenheit scale.

Question 15
Who invented Celsius scale of temperature?
Solution 15
Celsius invented the Celsius scale of temperature.
Question 16
Who invented Fahrenheit scale of temperature?
Solution 16
Fahrenheit invented the Fahrenheit scale of temperature.

Question 17
Name two liquid thermometers that are commonly used.
Solution 17
Mercury, alcohol are commonly used in thermometers.
Question 18
What is the principle used in a thermometer?
Solution 18
Thermometer works on the principal that substances expand when heated and contract on cooling.

Question 19
What is meant by the range of a thermometer?
Solution 19
Range of thermometer is the range of temperature which can be measured by thermometer.
Question 20
Name the liquid used in a clinical thermometer.
Solution 20
Mercury is the liquid used in a clinical thermometer

Question 21
What is the usual range of temperature marked on a clinical thermometer?
Solution 21
The usual range of temperature marked on clinical thermometer is 950 F to 1100F.
Question 22
Who designed the first thermometer?
Solution 22
Fahrenheit designed the first thermometer.

Question 23
What do you mean by calibration of a thermometer?
Solution 23
Before constructing a thermometer, we determine lower fixed point and upper fixed point and divide the whole range of thermometer into specific number of equal divisions to provide a scale for measuring the temperatures within a range.
Question 24
What is a clinical thermometer?
Solution 24
The clinical thermometer is specially designed thermometer used to measure the temperature of a human body easily and as accurately as possible.

## Chapter 5 - Heat - Thermometry Exercise 210

Question 1
Name two animals which are able to increase their body temperature in summers and decrease their body temperature in winters.
Solution 1
Camel and are two animals which are able to increase their body temperature in summers and decrease their body temperature in winters.
Question 2
Name the CGS unit of heat. Define it.
Solution 2
CGS unit of heat is Joule denoted by J.
1 J is amount of heat required to raise the temperature of a body by 1/4.12oC of temperature.

Question 3
Plot a graph taking 0C on the Y-axis and the corresponding 0F along the X-axis.
Solution 3
Question 4
Plot a graph taking 0F along the Y-axis and the corresponding 0C on the X-axis.
Solution 4

Question 5
Write the relationship between the Celsius and Fahrenheit scales of temperature.
Solution 5
Relation between Celsius and Fahrenheit scales of temperature is
C/100 = (F - 32)/180.
Question 6
State the temperature of ice point and steam point on the Fahrenheit scale.
Solution 6
Temperature of ice point on Fahrenheit scale =32oF.
Temperature of steam point on Fahrenheit scale =212o