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A room has a 4m x 4m x10cm concrete roof `(K_1 = 1.26w|m|'^oC)`. At some instant, the temperature outside is `46^oc` and radius `32^oc`. 1) Calculate amount of heat flowing per second into the room through the roof. 2) If bricks `(K_2 – 0.56w |m|'^oc)` of thickness 7.5cm are laid down on roof, calculate the new rate of heat flow under the same temperature

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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A bar of copper of length 75cm and a bar of length 125cm are joined end to end. Both are of circular cross – section with diameters 2cm. The free ends of copper and steel are maintained at `100^oc and 0^oc` respectively. The surfaces of the bars are thermally insulated. What is the temperature of copper – steel junction? Thermal conductivity of copper `= 9.2xx10^(-2)k cal |m|'^oc|s` and that of steel is `1.1xx10^(-2) k

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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If air is a bad conductor of heat, why do we not feel warm without

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A body with large reflectivity is a poor emitter

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Animals curl into a ball, when they feel very

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Why is it hotter at the same distance over the top of the fire than in front of

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A metal rod of length 20cm and diameter 2cm is covered with a non-conducting substance. One of it ends is maintained at `100^oc` while the other is at `0^oc`. It is found that 25g of ice melts in 5 min calculate coefficient of thermal conductivity of

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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Calculate the temperature in Kelvin at which a perfectly black body radiates at the rate of 5.67

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How do you derive Newton’s law of cooling from Stefan’s

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Define the terms reflectance, absorptance and transmittance. How are they

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Discuss briefly energy distribution of a black body radiation. Hence deduce wien’s displacement

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Estimate the fraction of molecular volume to the actual volume occupied by oxygen gas at STP. Take the diameter of an oxygen molecule to be 3

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Molar volume is the volume occupied by 1 mol of any (ideal) gas at standard temperature and pressure (STP : 1 atmospheric pressure, 0 °C). Show that it is 22.4

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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Figure shows plot of PV/T versus P for `1.00×10^(–3)` kg of oxygen gas at two different temperatures. (a) What does the dotted plot signify? (b) Which is true: T1 > T2 or T1< T2 ? (c) What is the value of PV/T where the curves meet on the y-axis? (d) If we obtained similar plots for 1.00×10–3 kg of hydrogen, would we get the same value of PV/T at the point where the curves meet on the y-axis? If not, what mass of hydrogen yields the same value of PV/T (for low pressure high temperature region of the

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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An oxygen cylinder of volume 30 litres has an initial gauge pressure of 15 atm and a temperature of 27 °C. After some oxygen is withdrawn from the cylinder, the gauge pressure drops to 11 atm and its temperature drops to 17 °C. Estimate the mass of oxygen taken out of the cylinder (R = 8.31 J `mol^(–1) K^(–1)`, molecular mass of O2 = 32

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An air bubble of volume 1.0 `cm^3` rises from the bottom of a lake 40 m deep at a temperature of 12 °C. To what volume does it grow when it reaches the surface, which is at a temperature of 35 °C

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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Estimate the total number of air molecules (inclusive of oxygen, nitrogen, water vapour and other constituents) in a room of capacity 25.0 `m^3` at a temperature of 27 °C and 1 atm

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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Estimate the average thermal energy of a helium atom at (i) room temperature (27 °C), (ii) the temperature on the surface of the Sun (6000 K), (iii) the temperature of 10 million kelvin (the typical core temperature in the case of a

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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Three vessels of equal capacity have gases at the same temperature and pressure. The first vessel contains neon (monatomic), the second contains chlorine (diatomic), and the third contains uranium hexafluoride (polyatomic). Do the vessels contain equal number of respective molecules ? Is the root mean square speed of molecules the same in the three cases? If not, in which case is vrms the largest

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At what temperature is the root mean square speed of an atom in an argon gas cylinder equal to the rms speed of a helium gas atom at – 20 °C ? (atomic mass of Ar = 39.9 u, of He = 4.0

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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