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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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Can you design heat energy of 100%

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Does the working of an electric refrigerator defy second law of

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A Carnot engine absorb `6×10^5` cal at `227^oc` calculate work done per cycle by the engine if it sink is at

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

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How does second law of thermodynamics explain expansion of

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Calculate difference in efficiency of a Carnot energy working between:-1) 400K and 350K2) 350K and

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Derive an expression for the work done during isothermal

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Briefly describe a Carnot cycle and derive an expression for the efficiency of Carnot

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

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What is an ideal perfect

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State Charles’s law? If air is filled in a vessel at `60^oc`. To what temperature should it be heated in order that `1/3^(rd)` of air may escape out of

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

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