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Introduction To Heat, Internal Energy And Work - Practice Questions & MCQ
Edited By admin | Updated on Sep 18, 2023 18:35 AM | #JEE Main
Quick Facts
-
42 Questions around this concept.
Solve by difficulty
A gas is compressed from a volume of to
at a constant pressure of
. During the compression, the gas releases
of heat to the surroundings. Calculate the work done by the gas.
A gas confined within a piston-cylinder assembly undergoes a process where it expands at constant pressure of from a volume of
During this process,
of heat is added to the gas. Calculate the work done by the gas and its change in internal energy.
Carnot Cycle Efficiency
An ideal heat engine operates on a Carnot cycle between a hot reservoir at and a cold reservoir at
. Calculate the efficiency of the engine.
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A piston-cylinder system contains 0.5 moles of an ideal gas initially at a pressure of and a volume of
.The gas undergoes an isothermal expansion at a constant temperature of
until its volume doubles. Calculate the work done by the gas during the expansion and the amount of heat transferred.
Given:
A thermodynamic system undergoes a cyclic process that consists of two steps. In the first step, the system absorbs of heat and performs
of work. In the second step, the system is brought back to its initial state by performing
f work. Determine the heat exchanged during the second step.
A refrigerator operates on a Carnot cycle between two reservoirs at temperatures . Calculate the coefficient of performance (COP) of the refrigerator.
A container holds of water initially at a temperature of
Heat is added to the water until its temperature reaches
Calculate the heat added to the water during this process.
Given the specific heat capacity of water is
A refrigerator operates on the reversed Carnot cycle. The cold reservoir temperature is and the hot reservoir temperature is
The refrigerator is used to cool an interior space to
Calculate the coefficient of performance (COP) of the refrigerator.
A heat engine operates between a hot reservoir at a temperature of 500 K and a cold reservoir at a temperature
of 300 K. What is the maximum theoretical efficiency of this heat engine?
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Download EBookAn ideal gas undergoes a reversible isobaric process. The initial volume is 40 liters, the initial temperature is , and the final temperature is
. Calculate the heat
added or removed from the gas during the process. Given the heat capacity at constant pressure
Concepts Covered - 2
Heat And Work
Heat
Heat is the energy transfer due to the difference in temperature. Heat is a form of energy which the system can exchange with the surroundings if they are at different temperatures. The heat flows from higher temperature to lower temperature.
Heat is expressed as 'q'
Heat absorbed by the system = +q
Heat evolved by the system = - q
Work
It is the energy transfer due to the difference in pressure that is, the mode of energy transfer.
Types of work
(i) Mechanical Work (Pressure volume work) = Force x Displacement
(ii) Electrical Work = Potential difference x charge flow , VQ = EnF
(iii)
(iv) Gravitational Work = mgh
Here m = mass of body,
g = acceleration due to gravity
h = height moved.
Units: dyne cm or erg (C.G.S.)
Newton meter (joule)
(i) If the gas expands, [V2> V1] and work is done by the system and W is negative.
(ii) If the gas [V2 < V1] and work is done on the system and W is positive.
Different Types of Works and the Formulas
(i) Work done in reversible isothermal process
(ii) Work done in irreversible isothermal process
Internal Energy
Internal Energy or Intrinsic Energy
The energy stored within a substance is called its internal energy. The absolute value of internal energy cannot be determined.
Or
It is the total energy of a substance depending upon its chemical nature, temperature, pressure, and volume, amount of substrate. It does not depend upon path in which the final state is achieved.
The exact measurement of it is not possible so it is determined as as follows:
Facts about Internal Energy
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It is an extensive property.
-
Internal energy is a state property.
-
The change in internal energy does not depend on the path by which the final state is reached.
-
Internal energy for an ideal gas is a function of temperature only so when the temperature is kept constant
is zero for an ideal gas.
-
For a cyclic process
is zero. (E = state function),
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For an ideal gas, it is totally kinetic energy as there is no molecular interaction.
-
Internal energy for an ideal gas is a function of temperature only hence, when the temperature is kept constant it is zero.
-
At constant volume (Isochoric)
-
For exothermic process,
but For endothermic process
-
It is determined by using a Bomb calorimeter of the system.
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