### Physics - Transference of Heat

#### Question - 1

The value of solar constant is

• A $1.937cal{ m }^{ -2 }{ s }^{ -1 }$
• B $1.937cal{ cm }^{ -2 }{ s }^{ -1 }$
• C $1.937\quad J{ m }^{ -2 }{ s }^{ -1 }$
• D $1.937\quad cal\quad c{ m }^{ -2 }\quad { minute }^{ -1 }$

#### Question - 2

The substance having lowest thermal conductivity is

• A air
• B copper
• C water
• D sand

#### Question - 3

All good conductors are

• A good reflectors
• C good absorbers
• D (a),(b) and (c) all are correct

#### Question - 4

Four identical bodies are painted differently. They are heated to the same temperature and then placed in an evacuated chamber to cool.The body cooling first will be that which was painted

• A shining black
• B rough black
• C shining white
• D rough white

#### Question - 5

Which of the following will cool rapidly?

• A A polished calorimeter filled with water at $100ºC$
• B A polished calorimeter filled with oil at $100ºC$
• C A black calorimeter filled with water at 100ºC
• D A black calorimeter filled with oil at 100ºC

#### Question - 6

Choose the INCORRECT statement

• A The process by which heat is transmitted from one part of a body to another by the actual movement of the particles themselves is called convection
• B The thermopile is an instrument for measuring radiation heat
• C The sun's heat reaches the earth by conduction, convection and radiation
• D Compared to a smooth surface, a rough surface is a better radiator of heat

#### Question - 7

A body at $0ºC$

• A does not emit any radiation
• C emits radiation of all those wavelengths which are emitted by it at room temperature
• D emits fewer wavelengths than it would at room temperature

#### Question - 8

The radiating power of a black body is E; the wavelength corresponding to the maximum energy density is ${ \lambda }_{ m }$the Stefan's constant is $\sigma$ and Wien's constant is b. The area A of the radiating surface of the body is

• A $A=\frac { 1 }{ \sigma } \left( \frac { { \lambda }_{ m } }{ b } \right) ^{ 4 }E$
• B $A=\sigma \left( \frac { b }{ { E }_{ m } } \right) ^{ 4 }E$
• C $A=\frac { 1 }{ \sigma } \left( \frac { b }{ { E }_{ m } } \right) { E }^{ 4 }$
• D NONE OF THE ABOVE

#### Question - 9

The S.I. unit of thermal conductivity is

• A $W{ m }^{ -2 }{ K }^{ -1 }$
• B $W{ m }^{ -1 }{ K }^{ -1 }$
• C $W{ m }^{ -1 }{ K }^{ -2 }$
• D $W{ m }^{ -2 }{ K }^{ -2 }$

#### Question - 10

Choose CORRECT statement

• A Diamond is a good thermal conductor
• B Diamond is a good electrical conductor
• C Diamond is a good electrical insulator
• D Both (a) and (c) are correct