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 = 0^oC + 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 98.4^oF.
We know C/100 = (F - 32)/180.
C =5/9(F- 32)
C = 5/9(98.4 - 32)
C = 5/9 X66.4
C =36.88^oC
Temperature of body of healthy man is 36.88^oC.

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 1^oC in Celsius scale is equal to rise of 1^oK 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 0^oC and 100^oC respectively. This range is divided into 100 equal divisions and each part gives 1^oC.

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 = -15^oC.
F = 9/5 X (-15) +32
F = -27 +32
F = 5^oF.

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 0^oK.
Temperature in Kelvin To K = Temperature in Celsius To C + 273.
0^oK = To C +273.
To C = -273^oC.
Absolute zero of temperature on Celsius scale is -273^oC.

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 = 1^oC.
We know C/100 = (F - 32)/180.
C =5/9(F- 32)
9/5C + 32 =F
F = 9/5C + 32.
So, difference of 1^o in Celsius scale is equal to the difference of 9/5^o in Fahrenheit scale.
Thus, Difference of 1^oC of temperature of two bodies in Celsius scale is equal to difference of 1.8^o 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 1/4.12^oC 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 =32^oF.
Temperature of steam point on Fahrenheit scale =212^o