At what temperature will oxygen molecules have the same root mean square speed as hydrogen molecules at 200 K?


Correct option is





 The value of ­vrms will be the same if




A Carnot’s engine working between 27oC and 127oC takes up 800 J of heat from the reservoir in one cycle. What is the work done by the engine?


A Carnot’s engine whose sink is at a temperature of 300 K has an efficiency of 40%. By how much should the temperature of the source be increased so as to increase the efficiency to 60%?


The surface of the earth receives solar radiation at the rate of 1400 Wm – 2. The distance of the centre of the sun from the surface of the earth is  m and the radius of the sun is  m. Treating the sun as a back body, it follows from the above data that the surface temperature of the sun is about


What is the SI unit of the Boltzmann’s constant?


Two slabs and B of different materials but of the same thickness are joined as shown in Fig. 8.8. The thermal conductivities of A and B are k1and k2 respectively. The thermal conductivity of the composite slab will be



A composite slap consists of two slabs A and of different materials but of the same thickness placed one on top of the other. The thermal conductivities of A and are k1 and k2 respectively. A steady temperature difference of 12oC is maintained across the composite slab. If k1 = k2/2, the temperature difference across slab A will be


Two cylindrical rods of lengths l1 and l2, radii r1 and r2 have thermal conductivities k1 and k2 respectively. The ends of the rods are maintained at the same temperature difference. If l1 = 2l2 and r1 = r2/2, the rates of heat flow in them will be the same if k1/k2 is


An ideal mono-atomic gas is taken around the cycle ABCDA as shown in the P-V diagram. The work done during the cycle is given by



If the temperature of a gas is increased from 27oC to 927oC, the root mean square speed of its molecules


743 J of heat energy is needed to raise the temperature of 5 moles of an ideal gas by 2 K at constant pressure. How much heat energy is needed to raise the temperature of the same mass of the gas by 2k at constant volume? Given, molar gas constant R = 8.3 J K – 1 mol – 1.