Zeroth law: If two bodies A and B are in thermal equilibrium and A and C are also in thermal equilibrium then B and C are also in thermal equilibrium.
First law of thermodynamics
∆U = ∆Q -∆W
Where
∆U = change in internal energy of a thermodynamic system
∆Q = Heat given to the system
∆W = work done by the system
Change in internal energy of a thermodynamic system is equal to the heat given to the system minus the work done by the system on surroundings or environment.
Second law of thermodynamics
Kelvin-Planck statement
It is not possible to design a heat engine which works in cyclic process and whose only result is to take heat from a body at a single temperature and convert it completely into mechanical work.
(Topic: Laws of Thermodynamics)
Showing posts with label Laws of thermodynamics. Show all posts
Showing posts with label Laws of thermodynamics. Show all posts
Monday, July 7, 2008
Thursday, April 24, 2008
Concept review Ch. 26 Laws of Thermodynamics
First law of thermodynamics
∆U = ∆Q -∆W
or ∆Q = ∆U + ∆W
In an ideal monatomic gas, the internal energy of the gas is simply translational kinetic energy of all its molecules.
the first law may be taken as a statement that there exists an internal energy function U that has a fixed value in a given state.
Remember that when work is done by the system,∆W is positive, If work is done on the system ∆W is negative.
When heat is given to the system ∆Q is positive. If heat is given by the system ∆Q is negative.
A positive ∆W decreases internal energy and a positive ∆Q increases internal energy.
Work done in an isothermal process on an ideal gas
W = nRTln(V2/V1)
Work done an isobaric process
W = p(V2-V1)
Work done an in isochoric process(volume of gas is constant)
zero
Second law of thermodynamics
Kelvin-Planck statement
It is not possible to design a heat engine which works in cyclic process and whose only result is to take heat from a body at a single temperature and convert it completely into mechanical work.
∆U = ∆Q -∆W
or ∆Q = ∆U + ∆W
In an ideal monatomic gas, the internal energy of the gas is simply translational kinetic energy of all its molecules.
the first law may be taken as a statement that there exists an internal energy function U that has a fixed value in a given state.
Remember that when work is done by the system,∆W is positive, If work is done on the system ∆W is negative.
When heat is given to the system ∆Q is positive. If heat is given by the system ∆Q is negative.
A positive ∆W decreases internal energy and a positive ∆Q increases internal energy.
Work done in an isothermal process on an ideal gas
W = nRTln(V2/V1)
Work done an isobaric process
W = p(V2-V1)
Work done an in isochoric process(volume of gas is constant)
zero
Second law of thermodynamics
Kelvin-Planck statement
It is not possible to design a heat engine which works in cyclic process and whose only result is to take heat from a body at a single temperature and convert it completely into mechanical work.
Friday, February 8, 2008
IIT JEE Physics Formula Revision 26. Laws of Thermodynamics
First law of thermodynamics and its applications (only for ideal gases) 26.1;
26.1 ΔU = ΔQ - ΔW or
ΔQ = ΔU + ΔW
26.2 ΔW =∫pΔV from V1 to V2
26.3 Work done in an Isothermal process:
W is given by the expression nRTln[V2/V1]
Work doen in an Isobaric process - pressure is constant
W = p[V2 - V1]
Work done in an isochoric process: volume is constant. No work is done by the system.
4. Efficiency of an engine
η = W/Q1 = 1 - Q2/Q1
Q1 = Amout of heat taken by the engine
Q2 = Heat rejected by the engine to low temperature bodies
5. Entropy
∆S = ∆Q/T
6. Sf - Si = ∫∆Q/T from i to f
26.1 ΔU = ΔQ - ΔW or
ΔQ = ΔU + ΔW
26.2 ΔW =∫pΔV from V1 to V2
26.3 Work done in an Isothermal process:
W is given by the expression nRTln[V2/V1]
Work doen in an Isobaric process - pressure is constant
W = p[V2 - V1]
Work done in an isochoric process: volume is constant. No work is done by the system.
4. Efficiency of an engine
η = W/Q1 = 1 - Q2/Q1
Q1 = Amout of heat taken by the engine
Q2 = Heat rejected by the engine to low temperature bodies
5. Entropy
∆S = ∆Q/T
6. Sf - Si = ∫∆Q/T from i to f
Tuesday, October 23, 2007
Study guide H C Verma JEE Physics Ch. 26 LAWS OF THERMODYNAMICS
JEE syllabus :
Equivalence of heat and work;
First law of thermodynamics and its applications (only for ideal gases) 26.1;
-------
Chapter sections
26.1 The first law of thermodynamics
26.2 Work done by a gas
26.3 Heat engines
26.4 The second law of thermodynamics
26.5 Reversible and irrerversible processes
26.6 entropy
27.7 Carnot engine
---------
Study plan
Day 1
26.1 The first law of thermodynamics
26.2 Work done by a gas
Day 2
26.3 Heat engines
Day 3
26.4 The second law of thermodynamics
26.5 Reversible and irrerversible processes
Day 4
26.6 entropy
27.7 Carnot engine
Day 5
Worked out examples 1 to 11
Day 6
Exercises 1 to 10
day 7
Exercises 11 to 20
Day 8
Exercises 21 to 22
Objective I
Day 9
Objective II
Questions for short answer 1 to 8
Day 10
Questions for short answer 9 to 15
Revision
Day 11
Concept review
Day 12
Formula revision
Days 13 to 20
Problems from test paper books
----------
Concepts covered
26.1 We already studied that heat is a form of energy. A system can be given energy either by supplying heat to it or by doing mechanical work on it.
Suppose in a process, an amount of ΔQ of heat is given to the gas and an amount ΔW of work is done by it.
Total energy of the gas must increase by ΔQ - ΔW. If the container along with the gas does not move (you can say that there is no systematic movement) this net energy must go into the system in the form of its internal energy.
If we denote the change in internal energy by ΔU, we can write
ΔU = ΔQ - ΔW or
ΔQ = ΔU + ΔW
The above equation is a mathematical statement of the first law of thermodynamics. The equation represents a statement of conservation of energy and is applicable to any system, however complicated.
The first law may be taken as a statement that there exists an internal energy function U that has a fixed value in a given state. Remember that internal energy is a state function.
Notation for ΔQ and ΔW
If work is done by the system, ΔW is positive. If work is done on the system ΔW is negative.
When heat is given to the system ΔQ is positive. If heat is given by the system to the surroundings ΔQ is negative.
Internal energy increases when heat is given to the system and work is done on the system.
26.2 Work done by a gas
In a cylindrical piston, if the gas expands by a small distance Δx, change in volume is ΔV which is equal to AΔx, where A is cross sectional area of cylinder or piston. As force is equal to pA work done is equal to
ΔW = p*A*Δx = p*ΔV = pΔV
Work done in expansion of from initial volume of V1 to V2 can be found by integrating pΔV and finding its definite integral value between V1 to V2.
ΔW =∫pΔV
This formual even though derived with cylindrical shape, is applicable to any shape.
Expressions for work done in various specified processes
Work done in an Isothermal process:
In an isothermal process Temperature is constant. Hence pV is constant.
For an ideal gas pV = nRT, therefore p = nRT/V
W is given by the expression nRTln[V2/V1]
Work done in an Isobaric Process
IN this process pressure is constant.
Hence W = p(V2-V1)
Work done in an Isocharic Process
As there is no change in volume of gas in this process, work done is zero.
26.5 Reversible and irrereversible processes
If the gas in thermal equilibrium all the parts of gas will be at the same temperature and the state of the gas can described by specifying its pressure, volume and temperature. If we put the container of gas on a hot stove, various parts of the gas will be at different temperatures and we cannot specify a unique temperature for the gas. The gas in not in thermodynamic equilibrium in this case.
If the process is performed in such a way that at any instant during the process the system is very nearly in thermodynamic equilibrium, the process is called quasi-static. Thus, a quasi static process is an idealized process in which all changes take place infinitely slowly. Such a process may be assumed to be reversible.
But a process can be reversible only if it satisfies two conditions. The process must be quasistatic and it should be nondissipative. This means, friction, viscosity etc. should be completely absent.
Reversible cycle: If all parts of cyclic process are reversible, it is called a reversible process.
-------------
Audiovisual lecture
Laws of thermodynamics
www.curriki.org/nroc/Introductory_Physics_1/lesson29/Container.html
Equivalence of heat and work;
First law of thermodynamics and its applications (only for ideal gases) 26.1;
-------
Chapter sections
26.1 The first law of thermodynamics
26.2 Work done by a gas
26.3 Heat engines
26.4 The second law of thermodynamics
26.5 Reversible and irrerversible processes
26.6 entropy
27.7 Carnot engine
---------
Study plan
Day 1
26.1 The first law of thermodynamics
26.2 Work done by a gas
Day 2
26.3 Heat engines
Day 3
26.4 The second law of thermodynamics
26.5 Reversible and irrerversible processes
Day 4
26.6 entropy
27.7 Carnot engine
Day 5
Worked out examples 1 to 11
Day 6
Exercises 1 to 10
day 7
Exercises 11 to 20
Day 8
Exercises 21 to 22
Objective I
Day 9
Objective II
Questions for short answer 1 to 8
Day 10
Questions for short answer 9 to 15
Revision
Day 11
Concept review
Day 12
Formula revision
Days 13 to 20
Problems from test paper books
----------
Concepts covered
26.1 We already studied that heat is a form of energy. A system can be given energy either by supplying heat to it or by doing mechanical work on it.
Suppose in a process, an amount of ΔQ of heat is given to the gas and an amount ΔW of work is done by it.
Total energy of the gas must increase by ΔQ - ΔW. If the container along with the gas does not move (you can say that there is no systematic movement) this net energy must go into the system in the form of its internal energy.
If we denote the change in internal energy by ΔU, we can write
ΔU = ΔQ - ΔW or
ΔQ = ΔU + ΔW
The above equation is a mathematical statement of the first law of thermodynamics. The equation represents a statement of conservation of energy and is applicable to any system, however complicated.
The first law may be taken as a statement that there exists an internal energy function U that has a fixed value in a given state. Remember that internal energy is a state function.
Notation for ΔQ and ΔW
If work is done by the system, ΔW is positive. If work is done on the system ΔW is negative.
When heat is given to the system ΔQ is positive. If heat is given by the system to the surroundings ΔQ is negative.
Internal energy increases when heat is given to the system and work is done on the system.
26.2 Work done by a gas
In a cylindrical piston, if the gas expands by a small distance Δx, change in volume is ΔV which is equal to AΔx, where A is cross sectional area of cylinder or piston. As force is equal to pA work done is equal to
ΔW = p*A*Δx = p*ΔV = pΔV
Work done in expansion of from initial volume of V1 to V2 can be found by integrating pΔV and finding its definite integral value between V1 to V2.
ΔW =∫pΔV
This formual even though derived with cylindrical shape, is applicable to any shape.
Expressions for work done in various specified processes
Work done in an Isothermal process:
In an isothermal process Temperature is constant. Hence pV is constant.
For an ideal gas pV = nRT, therefore p = nRT/V
W is given by the expression nRTln[V2/V1]
Work done in an Isobaric Process
IN this process pressure is constant.
Hence W = p(V2-V1)
Work done in an Isocharic Process
As there is no change in volume of gas in this process, work done is zero.
26.5 Reversible and irrereversible processes
If the gas in thermal equilibrium all the parts of gas will be at the same temperature and the state of the gas can described by specifying its pressure, volume and temperature. If we put the container of gas on a hot stove, various parts of the gas will be at different temperatures and we cannot specify a unique temperature for the gas. The gas in not in thermodynamic equilibrium in this case.
If the process is performed in such a way that at any instant during the process the system is very nearly in thermodynamic equilibrium, the process is called quasi-static. Thus, a quasi static process is an idealized process in which all changes take place infinitely slowly. Such a process may be assumed to be reversible.
But a process can be reversible only if it satisfies two conditions. The process must be quasistatic and it should be nondissipative. This means, friction, viscosity etc. should be completely absent.
Reversible cycle: If all parts of cyclic process are reversible, it is called a reversible process.
-------------
Audiovisual lecture
Laws of thermodynamics
www.curriki.org/nroc/Introductory_Physics_1/lesson29/Container.html
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