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What are the first and second Laws of Thermodynamics? 

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kimmie0322 | Student, Undergraduate | (Level 1) Honors

Posted June 20, 2012 at 11:19 PM via web

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What are the first and second Laws of Thermodynamics? 

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biditism | Student, Undergraduate | (Level 1) Honors

Posted June 21, 2012 at 9:00 AM (Answer #1)

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The first law of thermodynamics is the law of consrvation of energy. It expresses that heat and mechanical work is both the forms of energy and the can be interconverted. But their sum is always constant.

The second law is the law which governs the flow of heat and its conversion to mechanical work. It has many statements. It says that heat can only flow from higer temperature to lower temperature without external energy being added. It also says that entropy of a closed system cant decrease.

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jerichorayel | College Teacher | (Level 1) Senior Educator

Posted June 21, 2012 at 6:04 AM (Answer #2)

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First Law of thermodynamics: Energy is neither created nor destroyed it can only be transfered. This is the law of conservation of energy. While the energy is conserved, the internal energy f a system changes as the heat and work are transferedinthe system or out of the system.
Second Law of thermodynamics: Heat transfer. In any cyclic process the entropy will either increase or remain the same.
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elekzy | Student, Grade 11 | (Level 1) Valedictorian

Posted June 21, 2012 at 11:22 PM (Answer #3)

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1st law: Energy can neither be created nor destroyed but can be

            transferred from one form to another; total heat and energy 

            remains constant.

2nd law: heat always flows naturally from a hot object to a cold object

             but never from a cold object to a hot object.

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sanjeetmanna | College Teacher | (Level 3) Assistant Educator

Posted June 23, 2012 at 3:07 PM (Answer #4)

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First Law ....(conservation of energy)

Energy can neither be created neither destroyed but can be transformed from one form to another form, the toatal energy in the universe remain constant

Example - work done by the mechanical force...

Second law of thermodynamics..

Explain you about the direction of heat transfer...

it is impossible to extract an amount of heat from a hot reservoir and use it all to do work. Some amount of heat must be exhausted to a cold reservoir.

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belarafon | High School Teacher | (Level 2) Educator Emeritus

Posted June 28, 2012 at 6:31 PM (Answer #5)

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The first Law of Thermodynamics concerns the state of matter and energy. According to this law, there is a specific and finite amount of matter and energy in the universe, and that amount cannot be increased or decreased; instead, all matter and energy can be changed in form to one or the other, without ever losing the gross total of all matter/energy. Because of this, no system can ever put out more energy than it takes in, and no matter can ever be entirely destroyed.

The second Law of Thermodynamics concerns entropy, or the tendency for an isolated system to come to a stable state. Because the universe is a closed system, having a finite amount of matter/energy with no method of creating or destroying it, everything in the universe is moving towards a state of equilibrium, where all matter and energy are in the same physical state and the same temperature. This eventual fate is called the "Heat Death of the Universe," at which point there can be no motion because everything is in exactly the same state.


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