Thermal Properties of Matter Test

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Thermal Properties of Matter Test - 12

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Question 1
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Read the assertion and reason carefully to mark the correct option out of the options given below:
Assertion : A body that is a good radiator is also a good absorber of radiation at a given wavelength.
Reason : According to Kirchhoff's law the absorptivity of a body is equal to its emissivity at a given wavelength.

A
A. If both assertion and reason are true and the reason is the correct explanation of the assertion.

B
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

C
C. If assertion is true but reason is false.

D
D. If the assertion and reason both are false.

Solution

According to Kirchhoff's law, a = e. or the absorptivity of a body equals its emissivity. A good absorber is a good emitter. As a good absorber is poor reflector, emitting (or radiating) ability of body is oppositely related to its ability to reflect. Therefore good emitter (or radiator) is a poor reflector.
Question 2
1 / -0

Read the assertion and reason carefully to mark the correct option out of the options given below:
Assertion : Temperatures near the sea coast are moderate.
Reason : Water has a high thermal conductivity.

A
A. If both assertion and reason are true and the reason is the correct explanation of the assertion.

B
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

C
C. If assertion is true but reason is false.

D
D. If the assertion and reason both are false.

Solution

During the day when water is cooler than the land, the wind blows off the water onto the land (as warm air rises and cooler air fills the place). Also at night, the effect is reversed (since the water is usually warmer than the surrounding air on land). Due to this wind flow the temperature near the sea coast remains moderate.
Question 3
1 / -0

Read the assertion and reason carefully to mark the correct option out of the options given below:
Assertion : Bodies radiate heat at all temperatures.
Reason : Rate of radiation of heat is proportional to the fourth power of absolute temperature.

A
A. If both assertion and reason are true and the reason is the correct explanation of the assertion.

B
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

C
C. If assertion is true but reason is false.

D
D. If assertion is false but reason is true.

Solution

Assertion is false because at absolute zero (0, K), heat is neither radiates nor absorbed. Reason is the statement of Stefan’s law, as E ∝ T4.
Question 4
1 / -0

Read the assertion and reason carefully to mark the correct option out of the options given below:
Assertion : The equivalent thermal conductivity of two plates of same thickness in contact (series) is less than the smaller value of thermal conductivity.
Reason : For two plates of equal thickness in contact (series) the equivalent thermal conductivity is given by

A
A. If both assertion and reason are true and the reason is the correct explanation of the assertion.

B
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

C
C. If assertion is true but reason is false.

D
D. If the assertion and reason both are false.

Solution

Equivalent thermal conductivity of two equally thick plates in series combination is given by
if K1 < />
then K₁ < k="" />< />₂
Hence assertion and reason both are false.
Question 5
1 / -0

Read the assertion and reason carefully to mark the correct option out of the options given below:
Assertion : If the temperature of a star is doubled then the rate of loss of heat from it becomes 16 times.
Reason : Specific heat varies with temperature.

A
A. If both assertion and reason are true and the reason is the correct explanation of the assertion.

B
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

C
C. If assertion is true but reason is false.

D
D. If the assertion and reason both are false.

Solution

This is in accordance with the Stefan?s law E∝T⁴.
Question 6
1 / -0

Read the assertion and reason carefully to mark the correct option out of the options given below:
Assertion : Blue star is at high temperature than red star.
Reason : Wein's displacement law states that T∝(1/λ_m).

A
If both assertion and reason are true and the reason is the correct explanation of the assertion.

B
If both assertion and reason are true but reason is not the correct explanation of the assertion.

C
If assertion is true but reason is false.

D
If the assertion and reason both are false.

Solution

From Wein's displacement law, temperature (T)∝1/λ_m (where λ_m is the maximum wavelength). Thus temperature of a body is inversely proportional to the wavelength. Since blue star has smaller wavelength and red star has maximum wavelength, therefore blue star is at higher temperature then red star.
Question 7
1 / -0

Read the assertion and reason carefully to mark the correct option out of the options given below:
Assertion : A brass tumbler feels much colder than a wooden tray on a chilly day.
Reason : The thermal conductivity of brass is less than that of wood.

A
A. If both assertion and reason are true and the reason is the correct explanation of the assertion.

B
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

C
C. If assertion is true but reason is false.

D
D. If the assertion and reason both are false.

Solution

The thermal conductivity of brass is high i.e., brass is a good conductor of heat. So, when a brass tumbler is touched, heat quickly flows from human body to tumbler. Consequently, the tumbler appears colder, on the other hand wood is a bad conductor. So, heat does not flow from the human body to the wooden tray in this case. Thus it appears comparatively hotter.
Question 8
1 / -0

Read the assertion and reason carefully to mark the correct option out of the options given below:
Assertion : For higher temperature, the peak emission wavelength of a black body shifts to lower wavelengths.
Reason : Peak emission wavelength of a blackbody is proportional to the fourth power of temperature.

A
A. If both assertion and reason are true and the reason is the correct explanation of the assertion.

B
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

C
C. If assertion is true but reason is false.

D
D. If the assertion and reason both are false.

Solution

According to Wein's law, λ_mT = constant
Thus peak emission wavelength λ_m ∝ 1/T
Hence for higher temperature, peak emission wavelength for a black body shifts to lower wavelength.
Question 9
1 / -0

Read the assertion and reason carefully to mark the correct option out of the options given below:
Assertion : It is hotter over the top of a fire than at the same distance on the sides.
Reason : Air surrounding the fire conducts more heat upwards.

A
A. If both assertion and reason are true and the reason is the correct explanation of the assertion.

B
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

C
C. If assertion is true but reason is false.

D
D. If the assertion and reason both are false.

Solution

Heat is carried away from a fire sideways mainly by radiations. Above the fire, heat is carried by both radiation and by convection of air. The latter process carries much more heat.
Question 10
1 / -0

Read the assertion and reason carefully to mark the correct option out of the options given below:
Assertion : Woolen clothes keep the body warm in winter.
Reason : Air is a bad conductor of heat.

A
A. If both assertion and reason are true and the reason is the correct explanation of the assertion.

B
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

C
C. If assertion is true but reason is false.

D
D. If the assertion and reason both are false.

Solution

Woolen fibres encloses a large amount of air in them. Both wool and air are the bad conductors of heat and the coefficient of thermal conductivity is small. So, they prevent any loss of heat from our body.

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Thermal Properties of Matter Test - 12

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Thermal Properties of Matter Test - 12

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Question 1

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.

B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

C. If assertion is true but reason is false.

D. If the assertion and reason both are false.

Solution

Question 2

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.

B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

C. If assertion is true but reason is false.

D. If the assertion and reason both are false.

Solution

Question 3

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.

B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

C. If assertion is true but reason is false.

D. If assertion is false but reason is true.

Solution

Question 4

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.

B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

C. If assertion is true but reason is false.

D. If the assertion and reason both are false.

Solution

Question 5

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.

B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

C. If assertion is true but reason is false.

D. If the assertion and reason both are false.

Solution

Question 6

If both assertion and reason are true and the reason is the correct explanation of the assertion.

If both assertion and reason are true but reason is not the correct explanation of the assertion.

If assertion is true but reason is false.

If the assertion and reason both are false.

Solution

Question 7

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.

B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

C. If assertion is true but reason is false.

D. If the assertion and reason both are false.

Solution

Question 8

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.

B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

C. If assertion is true but reason is false.

D. If the assertion and reason both are false.

Solution

Question 9

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.

B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

C. If assertion is true but reason is false.

D. If the assertion and reason both are false.

Solution

Question 10

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.

B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

C. If assertion is true but reason is false.

D. If the assertion and reason both are false.

Solution

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