Mock Test

Heat and Thermodynamics part-(1)

by mocktest
Updated On:

Heat and Thermodynamics part-(1)

Total Questions: 45

31. Consider the following statements: [I.A.S. (PRE) 2022]

1. High clouds primarily reflect solar radiation and cool the surface of the Earth.
2. Low clouds have a high absorption of infrared radiation emanating from the Earth's surface and thus cause warming effect.
Which of the statements given above is/are correct?

Correct Answer: (d) neither 1 nor 2
Solution:Whether a given cloud will heat or cool the surface depend on several factors, including the cloud's altitude, its size, and the make-up of the particles that form the cloud. Low, thick clouds primarily reflect solar radiation and cool the surface of the Earth.

While high, thin clouds primarily transmit incoming solar radiation; at the same time, they trap some of the outgoing infrared radiation emitted by the Earth and radiate it back downward, thereby warming the surface of the Earth. Hence, both of the given statements are incorrect.

32. Consider the following statements: [I.A.S. (Pre) 2023]

Statement-I: The temperature contrast between continents and oceans is greater during summer that in winter.
Statement-II: The specific heat of water is more that that of land surface.
Which one of the following is correct in respect of the above statements?

Correct Answer: (a) Both Statement-I and Statement-II are correct and Statement-II is the correct explanation for Statement-I.
Solution:The specific heat capacity is the property of the substance which determines the change in the temperature of the substance (undergoing no phase change) when a given quantity of heat is absorbed (or rejected) by it. It is defined as the amount of heat per unit mass absorbed or rejected by the substance to change its temperature by one unit.

Water has the highest specific heat capacity compared to other substances. The specific heat of water is much greater than that of land surface. Owing to its high specific heat capacity, the water of ocean warms up much more slowly than the land during summer and consequently wind from the sea has a cooling effect.

On the other hand, the ocean slowly cools in winter keeping the air warm .That is the reason why the temperature contrast between continent and ocean is greater during summer than in the winter hence both of the statement 1 and the statement 2 is the correct explanation for the statement 1.

33. Fruit stored in a cold chamber exhibit longer storage life because [I.A.S. (PRE) 2013]

Correct Answer: (c) rate of respiration.
Solution:It is well known that the even after harvesting of the fruit the process of respiration continues and brings about the ripening change in colour softening of flesh increase in sugar content and development of flavour .

These changes occur more rapidly at higher temperature this means that the lower the temperature of storage the longer would be the storage life of the fruit. In cold chamber the rate of respiration of fruits is decreased.

34. Select the correct answer from the codes given below [U.P.P.C.S.(pre) 2001]

Assertion (A): Woollen clothes keeps us warm.
Reason (R) : Woollen fibres are made from a special type of protein, which is a bad conductor of heat.

Correct Answer: (c) (A) is true, but (R) is false.
Solution:Woollen clothes keep us warm in winter. It is just because woollen clothes have fibres and between those fibres, air is trapped which reduces heat loss. Air reduces heat loss because it is an insulator or poor conductor of heat. Thus statement (A) is correct but reason (R) is false.

35. Which one of the following statements is not correct? [I.A.S. (PRE) 2003]

Correct Answer: (c) The velocity of sound in air decreases as the humidity increases.
Solution:Humidity is the percentage of water vapour present in air. As the humidity increases, the percentage of water vapour in air increase and this decreases the density of air. This results in the increase of velocity of sound. So increase in the humidity of air increases the velocity of sound in air. Thus, statement (c) is not correct.

36. Opening the door of refrigerator kept in the room [39th B.P.S.C. (PRE) 1994]

Correct Answer: (c) You can warm the room a little.
Solution:If the door of a refrigerator kept open in a room, the temperature will start to rise inside the refrigerator. The thermostat will kick in and try to cool it back down. This means the motor is running, which means heat is being added to the room resulting warmer room.

37. If the doors of a refrigerator are left open for few hours, then the room temperature will: [67th B.P.S.C. (Pre) 2022]

Correct Answer: (b) increase
Solution:If the door of a refrigerator kept open in a room, the temperature will start to rise inside the refrigerator. The thermostat will kick in and try to cool it back down. This means the motor is running, which means heat is being added to the room resulting warmer room.

38. Which of the following scales of temperature does not have a negative value ?

Correct Answer: (c) kelvin
Solution:The kelvin scale has no negative values.The kelvin scale is the best representation of average kinetic molecular energy when a substance has a temperature of 0k (-273.15 degree celsius) it is at absolute zero and has no kinetic energy all because its particles stop moving .

39. A measured temperature in fahrenheit scale is 200°F. what will be its value in celsius scale ? [U.P.B.E.O. (PRE) 2019]

Correct Answer: (a) 93.3°C
Solution:The formula  to convert Fahrenheit (°F) to celsius (°C) is

C=(F-32)×5/9

since the temperature in °F=200°F

∴ C=(200-32)×5/9

=168×5/9=840/9=93.3

so the value of 200°F is 93.3°C  in celsius scale.

40. The value of 40 degrees celsius in Fahrenheit scale is : [64th B.P.S.C. (PRE) 2018]

Correct Answer: (a) 104°F
Solution:F=(9/5)×C+32
where C=centigrade temperature
F=Fahrenheit Temperature⇒
F=(9/5)×40+32 ⇒F=72+32⇒F=104
so the value of 40°C is 104°F at Fahrenheit scale.

mocktest

Related Articles

CHEMISTRY (Part-V) (Railway)

Defence Technology Part-1

Space Part-4

Space Part-3

Space Part-2

Space Part-1

Leave a Comment