NCERT Solutions for class 11 Physics | Chapter 11 - Thermal Properties of Matter

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Questions
1 A person with dark skin as compared to a person with white skin will experience
A Less heat and less cold
B More heat and more cold
C More heat and less cold
D Less heat and more cold.

Answer:More heat and more cold
2 The best ideal black body is
A Lamp of charcoal heated to high temperature
B Metal coated with a black dye
C Glass surface coated with coalter
D Hollow enclosure blackened inside and having a small hole

Answer:Hollow enclosure blackened inside and having a small hole
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3 The process of heat transfer in which heat is transferred with actual migration of medium particles is known as (AFMC-94)
A Conduction
B Convection
C Radiation
D Reflection

Answer:Convection
4 The flow of heat from a hot body to a cold body is an example of
A Isothermal process
B Reversible process
C Adiabatic process
D Irreversible process

Answer:Irreversible process
5 A black body at hot temperature at 227°C radiates heat at a rate of 5 cal/cm²s. at a temperature of 727°C the rate of heat radiated per unit area will be
A 50 cal/cm²s
B 250 cal/cm²s
C 80 cal/cm²s
D 100 cal/cm²s

Answer:80 cal/cm²s
6 A bucket full of hot water is kept in a room and it cools from 75°C to 70°C in t1 minutes from 70°C to 65°C in t2 minutes and from 65°C to 60°C in t3 minutes; then
A t1 – t2 = t3
B t1 < t2 < t3
C t1 > t2 > t3
D t1 < t2 > t3

Answer:t1 < t2 < t3
7 Two stars A and B radiate maximum energy at 3600°A and 3600°A respectively. Then the ratio of absolute temperatures of A and B is
A 256 : 81
B 81 : 256
C 3 : 4
D 4 : 3

Answer:4 : 3
8 A cup of tea cools from 80°C to 60°C in one minute. The ambient temperature is 30°C. in cooling from 60°C to 50°C, it will take.
A 50 sec
B 90 sec
C 60 sec
D 30 sec

Answer:50 sec
9 Unit of Stefans constant is given by
A W/ m K²
B W/ m² K²
C W²/ m² K4
D W/ mK

Answer:W/ m² K²
10 The earth receives at its surface radiation from the sun at the rate of 1400 W/m². the distance of the centre of the sun from the surface of the earth is 1.5 1011 m and the radius of the sun is 7.0 108 m. treating sun as a black body, it follows from the above data that its surface temperature is,
A 5801 K
B 106 K
C 50.1 K
D 2801 C

Answer:5801 K
11 The temperature of a piece of metal is raised from 27°C to 51.2°C. the rate at which metal radiates energy increases nearly
A 1.36 times
B 2.36 times
C 3.36 times
D 4.36 times

Answer:1.36 times
12 The earth intercepts approximately one billionth of the power radiated by the sun. if the surface temperature of the sun were to drop by a factor of 2, the average radiant energy incident on earth per second would reduce by factor of
A 2
B 4
C 8
D 16

Answer:16
13 Emissivity of perfectly black body is
A 1
B 2
C 5
D 0

Answer:1
14 A body cools from 50°C to 46°C in 5 minutes and to 40°C in the next 10 minutes. The surrounding temperature is
A 30°C
B 28°C
C 36°C
D 32°C

Answer:30°C
15 Absorptive power of perfectly black body is
A Zero
B Infinity
C One
D Constant

Answer:One
16 For which of the following process, the thermal conduction is maximum?
A Combustion
B Radiation
C Convection
D Conduction

Answer:Radiation
17 A metal piece heated to T1°K. The temperature of the surrounding is T2°K. the heat in the surrounding due to radiation is proportional to
A (T14 – T24)
B (T1 – T2)4
C (T14 + T24)
D (T13 – T23)

Answer:(T14 – T24)
18 A surface at temperature T0°K receives power P by radiation from a small sphere at temperature T >> T0 and at a distance d. if both T and d are doubled, the power received by surface will becomes approximately
A P
B 2p
C 4p
D 16p

Answer:4p
19 The good absorber of heat are
A Non-emitter
B Poor-emitter
C Good-emitter
D Highly polished

Answer:Good-emitter
20 Co-efficient of reflection, coefficient of absorption and coefficient transmission are related as
A a + r + 1 = 1
B a + r + t1 1
C a + r = -t
D a1 r + 1

Answer:a + r + 1 = 1

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