### Heat and thermodynamics

57. The material of least linear expansivity is **[2075]**

Aluminum

Invar

Steel

Nickel

58.A glass vessel contains air at 27°C the temperature to which it must be
heated so that one-fourth of air is expelled from it at constant pressure is**[2075]**

47°C

77°C

102°C

127°C

59.The efficiency of heat engine will be 100% if the temperature of sink is**[2075]**

0K

0°C

equal to source

none of above

60. A cylinder of 0.6 m long and 6mm radius is rated at 1.5 kW.the temperature of filament if Stefan’s constant is 6 x 10^{-8} Wm ^{-2}K ^{-4}**[2075]**

920K

1125K

1025K

1320K

56. If a 200m bridge of steel has length from, temperature varies from 243K us 313K, The change of length of bridge for above seasonal variation in temperature (α_{steel} = 11 × 10^{-6}) **[2074]**

15.4 cm

15.9 cm

15.8 cm

10 cm

57. Internal Energy of perfect gas does not change during **[2074]**

adiabatic process

isothermal process

isobaric process

Isochoric process

58. Efficiency of steam engine is of order of **[2074]**

10%

20%

60%

100%

59. A gas maximum works when it expands **[2074]**

isothermally

isobarically

adiabatically

isochorically

58. The temperature of a substance increase by 270°C. This increase is equal to **[2073]**

300k

0k

27k

273k

59. Which of the following gases possess maximum rans speed at a given
temperature? **[2073]**

H_{2}

N_{2}

O_{2}

H_{6}

60. The black body emits **[2073]**

Line spectrum

band spectrum

continuous spectrum

mixed spectrum

59. A square plate of side 2 units is heated through 10°C. If the linear exansivity of the material is x, increase in the surface area of the plate is **[2072]**

480x

80x

240x

240x^{2}

60. A black body radiates heat energy at the rate of 2 x 10 Js''m' at a temperature of 127°C. The temperature of the black body at which the rate of heat radiation is 32 x 10^{5} is **[2072]**

327°

927°

527°

727°