One mole of an ideal gas expands adiabatically from temperature T1 to temperature T2. The work done by the gas is
We have ΔU = ∫(T2 to T1) CvdT − Cv(T2−T1)
Since the process is adiabatic, dQ = 0
ΔQ = ΔU + ΔW
ΔQ = ΔU + ΔW
∴ ΔW = −ΔU
The pressure-volume graph of an ideal gas cycle consisting of isothermal and adiabatic process is shown in the figure. The adiabatic process is described by
BC and DA represent the adiabatic expansion and the compression since we know that the adiabatic curves are more steeper than isothermal curves.
The correct answer is: AD and BC
A water fall is 168m high. Assuming that half the kinetic energy of the falling water gets converted into heat, the rise in temperature of water is approximately (take g = 10m/s2)
The correct answer is: 0.2ºC
One gram of water on evaporation at atmospheric pressure forms 1671cm3 of steam. Heat of vaporization at this pressure is 540 cal/g. Calculate the increase in the internal energy. (Atmospheric pressure = 1×105N/m2)
A sample of gas expands from volume V1 to V2. The amount of work done by the gas in greatest when the expansion is.
pV curves for 3 processes are show is below. Note that the area under isobaric curve is maximum
The correct answer is: isobaric
One gram of water on evaporation at atmospheric pressure forms 1671cm3 of steam. Heat of vaporization at this pressure is 540 cal/g. The increase in internal energy is
The correct answer is: 500 cal
Heat capacity of a substance is infinite. It means :
A system changes from the state (p1, V1 ) to the state (p2, V2 ) as shown in the figure. The work done by the system is.
Work done = Area of graph ABD;
From above we get,
Area = 1/2 × 4 (1 × 105 + 5 × 105) = 2 × 6 × 105 = 12 × 105J
A body of mass 25kg is dragged on a rough horizontal road for one hour with a speed of 20km/hr.
If the coefficient of friction is 0.5 and half of the heat produced is absorbed by the body, the rise in its temperature is (specific heat of body = 0.1cal/g ºC, g = 10m/s2)
Distance traveled in one hour,
S = 20km
The correct answer is: 119ºC
A gas, for which γ is 4/3, is heated at constant pressure. The percentage of heat supplied used for external work.
The correct answer is: 25%