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Assignment 2 on subjective type questions on heat and thermodynamics



Question 1:
A composite slab is prepared by pasting three slab of thickness L1,L2,L3 and thermal conductivity K1,K2,K3.The slab have equal cross-sectional area .Find the equivalent thermal conductivity
a.K1K2K3(L1+L2+L3)/K2K3L1+K1K3L2+K1K2L3
b.K2K3L1+K1K3L2+K1K2L3/K1+K2+K3
c. K1+K2+K3/L1+L2+L3
d. L1+L2+L3/K1+K2+K3
Question 2:
Three black bodies are such that higher intensity wavelengths are in the ratio
     λm1 : λm2 : λm3 = 1 :(21)1/2: (3)1/2
     which of the these is true for the temperatures
a,     T1 > T3 > T2          b,     T1 > T2 > T3
c,     T3 > T2 > T1          d,     T3 > T1 > T2     Question 3:
The tungsten element of the electric lamp has as surface area A and Power is P and emissivity is 0.4
a. Find the temperature of the filament
b. if the tungsten filament behave like blackbody ,find the % increase in power required to maintain the same temperature.
Question 4:
A Rod is initially at a uniform temperature at T1.One end is kept at T1 and other end is kept in a furnace maintained at temperature at T2.(T2 >T1).The Surface of the rod is insulated so that heat can flow lengthwise along the red-Light of the Rod is L, area A and thermal conductivity of the Rod is K. Consider a short cylindrical element of the rod of unit length .If the temperature gradient at the one end of the element is K' . Find the rate of flow across the element.
Question 5:
 A gas mixture consist of molecules of type A, B, C, D with molecular
     masses Ma > Mb > Mc >Md
     Two statement are drawn from it
A, Average kinetic energy of four type of gases in the mixture are in the ratio
     Ea/1 =Eb/1 =Ec/1 =Ed/1
B, Rms speed of molecules of the four types are in the order if V is the rms speed
     VD > VC > VC > VA
     which one of following is true
a,     Only A correct               b,     Only B correct
c,     A & B both are correct               d,     A & B both are wrong
Question 6:
Calculate the variation of atmospheric pressure with elevation of the earth atmosphere. Considering the temperature to be uniform throughout(which is not the actual case)
Question 7:
An ideal gas sample of .203 gm occupies 1000cm3 at STP. Calculate the RMS speed of the molecules
Question 8:
How will the rate of collision of a rigid diatomic molecules against the vessel will change ,if the gas is expanded adiabatically η times
Question 9:
Which one of the following statement is true about a gas undergoing isothermal change
a) The temperature of the gas is constant
b) The pressure of the gas  remains constant
c) the volume of the gas remains constant
d) The gas is completely insulated from the surrounding’s
Question 10:
Which of the following devices is used to detect thermal radiation?
a)Thermopile
b) Constant volume air thermometer
c) Liquid thermometer
d) Six Maximum and minimum thermometer


Solutions

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