Thermal Physics Quiz 11

C

Thermal Physics Quiz-11

Dear Readers,

As per analysis for previous years, it has been observed that students preparing for NEET find Physics out of all the sections to be complex to handle and the majority of them are not able to comprehend the reason behind it. This problem arises especially because these aspirants appearing for the examination are more inclined to have a keen interest in Biology due to their medical background. Furthermore, sections such as Physics are dominantly based on theories, laws, numerical in comparison to a section of Biology which is more of fact-based, life sciences, and includes substantial explanations. By using the table given below, you easily and directly access to the topics and respective links of MCQs. Moreover, to make learning smooth and efficient, all the questions come with their supportive solutions to make utilization of time even more productive. Students will be covered for all their studies as the topics are available from basics to even the most advanced. .

Q1.  Of the following thermometers, the one which can be used for measuring a rapidly changing temperature is a:

•  Thermocouple thermometer
•  Gas thermometer
•  Maximum resistance thermometer
•  Vapour pressure thermometer

Solution
Rapidly changing temperature is measured by thermocouple thermometers

Q2. Temperature of a black body increases from 327℃ to 927℃, the initial energy possessed is 2KJ, what is its final energy

•  32 KJ
•  320 KJ
•  1200 KJ
•  None of these

Solution

Q3. The amount of radiation emitted by a perfectly black body is proportional to:

•  Temperature of ideal gas scale
•  Fourth root of temperature on ideal gas scale
•  Fourth power of temperature on ideal gas scale
•  Source of temperature on ideal gas scale

Solution
E∝T⁴ (Stefan’s law)

Q4. A metal rod AB of length 10x has its one end A in ice at 0℃ and the other end B in water at 100℃. If a point P on the rod is maintained at 400℃, then it is found that equal amounts of water and ice evaporate and melt per unit time. The latent heat of evaporation of water is 540 cal/g latent heat of melting of ice is 80 cal/g. If the point P is at a distance of λx from the ice end A, find the value of λ. [Neglect any heat loss to the surrounding]

•  9
•  2
•  6
•  1

Solution

Q5.  Consider a compound slab consisting of two different materials having equal lengths, thicknesses and thermal conductivities K and 2K respectively. The equivalent thermal conductivity of the slab is

•  √2K
•  3K
•  4/3 K
•  2/3 K

Solution
 Equivalent thermal conductivity of the compound, slab,

Q6. A thin square steel plate with each side equal to 10 cm is heated by a blacksmith. The rate of radiated energy by the heated plate is 1134 W. The temperature of the hot steel plate is (Stefan’s constant σ=5.67×10^-8 watt m^-2 K^-4, emissivity of the plate = 1).

•  1000 K
•  1189 K
• 2000 K
•  2378 K

Solution
The rate of radiated energy Q/t=P=AεσT⁴ ⇒1134=5.67×10^-8×(0.1)² T⁴⇒T=1189 K .

Q7. Two substances A and B of equal mass m are heated at uniform rate of 6 cal s^-1 under similar conditions. A graph between temperature and time is shown in figure. Ratio of heat absorbed H_A/H_B by them for complete fusion is

•  9/4
•  4/9
•  8/5
•  5/8

Solution
From given curve, Melting point for A=60℃ And melting point for B=20℃ Time taken by A for fusion =(6-2)=4 minute Time taken by B for fusion =(6.5-4)=2.5 minute

Q8. Two metal strips that constitute a thermostat must necessarily differ in their

•  Mass
•  TLength
•  Resistivity
•  Coefficient of linear expansion

Solution
Thermostat is used in electric apparatus like refrigerator, iron etc for automatic cut off. Therefore for metallic strips to bend on heating their coefficient if linear expansion should be different.

Q9.  On a clear sunny day, an object at temperature T is placed on the top of a high mountain. An identical object at the same temperature is placed at the foot of mountain. If both the objects are exposed to sun-rays for two hours in an identical manner, the object at the top of the mountain will register a temperature

•  Higher than the object at the foot
•  Lower than the object at the foot
•  Equal to the object at the foot
•  None of the above

Solution
Because of uneven surfaces of mountains, most of it’s parts remain under shadow. So, most of the mountains, land is not heated up by sun rays. Besides this, sun rays fall slanting on the mountains and are spread over a larger area. So, the heat received by the mountains top per unit area is less and they are less heated compared to planes (Foot)

Q10. On which of the following scales of temperature, the temperature is never negative:

•  Celsius
•  Fahrenheit
•  Reaumur
• Kelvin

Solution
Zero kelvin =-273℃ (absolute temperature). As no matter can attain this temperature, hence temperature can never be negative on Kelvin scale