First Law of Thermodynamics

IMPORTANT

First Law of Thermodynamics: Overview

This topic covers concepts such as Sign Convention in Thermodynamics, First Law of Thermodynamics, First Law of Thermodynamics in Isochoric Process, Heat in Isochoric Process, First Law of Thermodynamics in Isobaric Process, etc.

Important Questions on First Law of Thermodynamics

EASY
IMPORTANT

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

MEDIUM
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When heat is supplied to the system then ΔQ is ____ and ΔQ is ____ when heat is extracted from the system. Choose the appropriate option.

EASY
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The ratio of work done by an ideal monoatomic gas to the heat supplied to it in an isobaric process is

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IMPORTANT

When a system is taken from state i to state f along the path iaf, it is found that Q=50 cal and W=20 cal. Along the path ibfQ=36 cal and Walong the path ibf is

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The P-V diagram of a system undergoing thermodynamic transformation is shown in figure. The work done by the system in going from ABC is 30 J and 40 J heat is given to the system. The change in internal energy between A and C is

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EASY
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A sample of liquid in a thermally insulated container (a calorimeter) is stirred for 2 hours, by a mechanical linkage to a motor in the surrounding, for this process:

HARD
IMPORTANT

Two moles of a monatomic ideal gas are taken through a cyclic process shown on the P-T diagram. The process CA is represented as PT = constant. If the efficiency of the given cyclic process is 1-x12ln2+15, then what is the value of x?

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HARD
IMPORTANT

A spherical bubble inside water has radius R. Take the pressure inside the bubble and the water pressure to be p0.The bubble now gets compressed radially in an adiabatic manner so that its radius becomes (R-a). For a<<R the magnitude of the work done in the process is given by 4πp0Ra2X,, where X is a constant and γ=CPCv=4130. The value of X is _______ correct to nearest integer.

MEDIUM
IMPORTANT

A thermodynamic cyclic process has been depicted in the adjoining P-V diagram. It is given that the heat absorbed and work done by the system along the path ABC is 90 J and 30 J, respectively. If the amount of work done along the path ADC is 20 J, then what will be the amount of heat absorbed in J along the same path?

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MEDIUM
IMPORTANT

1 mole of rigid diatomic gas performs a work of Q5 when heat Q is supplied to it. The molar heat capacity of the gas during this transformation is xR8. The value of x is ________ .

MEDIUM
IMPORTANT

A monatomic ideal gas undergoes a process ABC. The heat given to the gas is,

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MEDIUM
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For free expansion of the gas which of the following is true

MEDIUM
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A 4-mol ideal gas system undergoes an adiabatic process where it expands and does 20 J of work on its environment. How much heat is received by the system?

MEDIUM
IMPORTANT

Which of the following is equivalent to the principle of energy conservation?

HARD
IMPORTANT

An ideal gas undergoes change in its state from the initial state l to the final state F via two possible paths as shown below. Then,

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HARD
IMPORTANT

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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HARD
IMPORTANT

A resistance coil, connected to an external battery, is placed inside an adiabatic cylinder (whose axis is vertical). The cylinder is fitted with a frictionless piston of mass m and trapping an ideal mono-atomic gas. A constant current i flows through the coil of resistance R. Neglect the atmospheric pressure. It is observed that the piston moves slowly and with constant speed. That constant speed is

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MEDIUM
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The workdone on the system in changing the state of a gas adiabatically from equilibrium state A to equilibrium state B is 32.4 J. If the gas is taken from state A to B through another process in which the net heat absorbed by the system is 13.5 cal, then the net workdone by the system in the later case is 1 cal=4.2 J

EASY
IMPORTANT

An electric heater supplies heat to a system at a rate of 100 W. If the system performs Work at a rate of 60 joules per second, the rate at which internal energy changes is

MEDIUM
IMPORTANT

Two cylinders A and B of equal capacity are connected to each other via a stopcock. A contains an ideal gas at standard temperature T1 and pressure. B is empty. Then the entire system is thermally insulated. The stopcock is suddenly opened. After the gas reaches equilibrium the temperature T2 of the gas measured. Which of the following is correct?