First Law of Thermodynamics

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First Law of Thermodynamics: Overview

This topic covers concepts such as Isotherm, Sign Convention in Thermodynamics, Equation for Work Done, First Law of Thermodynamics, Work Done by Thermodynamic System, Internal Energy in Thermodynamics, etc.

Important Questions on First Law of Thermodynamics

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An ideal monoatomic gas is confined in a horizontal cylinder by a spring loading piston (as shown in Fig 20.63). Initially the gas is at temperature T1 pressure P1 and volume V1 and the spring is in relaxed state. The gas is then Fig. 20.63 heated very slowly to temperature T2, pressure p2 and volume V2. During this process the piston moves out by a distance X. Ignoring the friction between the piston and the cylinder, the correct statements s is (are)

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For the following two isotherms drawn at two different temperature T1 and T2 which of the following statement is true? ( number of moles are constant )

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An ideal gas at 27°C is compressed adiabatically to 827 of its original volume. The rise in temperature is (Take γ =53)

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Show that slope of adiabatic curve is γ times the slope of isothermal process.

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The slope of isothermal and adiabatic curves are related as

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The graph for Boyle's law is called

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An ideal gas is allowed to expand freely against vacuum in a rigid insulated container. The gas undergoes

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An ideal is filled in a closed, rigid and thermally-insulated container. A coil of 100Ω resistance and carrying a current of 1 A supplies heaT to the gas. The change in the internal energy of the gas after 5 minutes will be:

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During an adiabatic expansion, a gas does 50 J of work against the surroundings. It is then cooled at constant volume by removing 20 J of energy from the gas. The magnitude of the total change in internal energy of the gas is x J. The value of x is

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A rigid diatomic ideal gas undergoes an adiabatic process at room temperature. The relation between temperature and volume for this process is TVx= constant, then x  is:

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A cycle tyre bursts suddenly. What is the type of this process?

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One mole of helium is adiabatically expanded from its initial state pi,Vi,Ti to its final state pf,Vf,Tf. The decrease in the internal energy associated with this expansion is equal to

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A container of volume 1 m3 is divided into two equal compartments by a partition. One of these compartments contains an ideal gas at 300 K. The other compartment is vacuum. The whole system is thermally isolated from its surroundings. The partition is removed in the gas container. Its temperature now would be

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Six moles of an ideal gas performs a cycle shown in the figure. If the temperatures are TA=600 K, TB=800 K, TC=2200 K and TD=1200 K, then work done per cycle is approximately___ (Take R=8.3 J mol-1 K-1)

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Two identical cylinders A and B with frictionless pistons contain the same ideal gas at the same temperature and the same volume V. The mass of the gas in A is mA and that in B is mB. The gas in each cylinder is now allowed to expand isothermally to the same final volume 2V. The change in the pressure in A and B are found to be P and 1.5 P respectively. Then

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P-V plots for two gases during adiabatic processes are shown in the figure. Plots 1 and 2 should correspond respectively to:

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In adjoining diagram, no heat exchange between the gas and the surroundings will take place if the gas is taken along:

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One mole of an ideal gas at pressure P0 and temperature T0 volume V0 is expanded isothermally to twice its volume and then compressed at constant pressure to V0/2 and the gas is brought to its original state by a process in which PV (Pressure is directly proportional to volume). The correct representation of the process is

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One mole of an ideal monatomic gas is taken through a semicircular thermodynamic process ACB shown in the PV diagram. The heat supplied to the system is

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One mole of an ideal gas is taken through the process, ABC as shown in the figure. The temperature of the gas at A is T0​.The total work done on the gas is,

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