Mechanical equivalent of heat - Revision history

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[[Category:Done 2018-07-20]]
[[File:Joule's Apparatus (Harper's Scan).png|340px|thumbnail|Figure 1: James Joule's famous experiment which demonstrated the mechanical equivalence of heat.<ref>Wikimedia Commons [Online], Available: http://upload.wikimedia.org/wikipedia/commons/c/c3/Joule%27s_Apparatus_%28Harper%27s_Scan%29.png</ref>]]
<onlyinclude>[[Mechanical energy]] can be converted into [[heat]], and heat can be converted into some mechanical energy. This important physical observation is known as the '''mechanical equivalent of heat'''. This means one can change the [[internal energy]] of a system by either doing [[work]] to the system, or adding heat to the system. This concept is fundamental to [[thermodynamics]] which applies the ideas of heat and work in order to create useful systems such as [[engine]]s, [[power plant]]s, and [[refrigerator]]s.</onlyinclude> This equivalence of heat and motion was tested in a classic experiment by James Joule in 1843, who used the change in [[potential energy]] of falling masses to stir water.<ref>Hyperphysics, ''Mechanical equivalence of heat'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/heat.html#c3</ref> The water increased in [[temperature]], much like it would when put over a flame. This showed that the downward motion of the masses which caused the water to be stirred (a form of mechanical motion) could in fact be equated to an increase in water temperature—or an increase in the heat,

This idea of work and heat equivalence is stated in the [[First law of thermodynamics]], which says that the change in internal energy of a system is the sum of the work done and the heat added to any system. From this, if a system is observed at any state, it is impossible to tell whether it reached this state from an input of work, an input of heat, or a combination of the two.<ref>M. Zemansky, ''The Use and Misuse of the Word "Heat" in Physics Teaching'' [PDF], Available: https://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0CCcQFjAB&url=http%3A%2F%2Fsciphy.tistory.com%2Fattachment%2Fcfile24.uf%401810D1264C95C1266B5C98.pdf&ei=echHVfSeB8TFogT2zYD4DA&usg=AFQjCNEuSqEa3mSsrbe8BadaguDYUmL0RQ&sig2=bSEKcMTJ8bPm5nyHUCciCg&bvm=bv.92291466,d.cGU</ref> This is shown in Figure 2 below.

[[File:Equivalence of heat.gif|center|600px|thumbnail|Figure 2: It is impossible to distinguish between work and heat when observing the final state of a system<ref>Hyperphysics, ''Heat and Work Example'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/heat.html#c2</ref>]]

==For Further Reading==
*[[Mechanical energy]]
*[[Energy conversion technology]]
*[[Thermal energy]]
*[[Heat]]
*[[Work]]
*[[Pressure volume diagram]]
*Or explore a [[Special:Random|random page]]

==References==
{{reflist}}
[[Category:Uploaded]]

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J.williams at 16:56, 12 August 2015

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[[Category:Done 2015-06-01]]
[[File:Joule's Apparatus (Harper's Scan).png|340px|thumbnail|Figure 1: James Joule's famous experiment which demonstrated the mechanical equivalence of heat.<ref>Wikimedia Commons [Online], Available: http://upload.wikimedia.org/wikipedia/commons/c/c3/Joule%27s_Apparatus_%28Harper%27s_Scan%29.png</ref>]]
<onlyinclude>'''Mechanical equivalent of heat''' is the notion that [[mechanical energy]] can be converted into [[heat]], and vice versa. That is, one can change the [[internal energy]] of a system by either doing [[work]] to the system, or adding heat to the system. This concept is fundamental to [[thermodynamics]] which applies the ideas of heat and work in order to create useful systems such as [[engine]]s, [[power plant]]s, and [[refrigerator]]s.</onlyinclude> This equivalence of heat and motion was tested in a classic experiment by James Joule in 1843, who used the change in [[potential energy]] of falling masses to stir water.<ref>Hyperphysics, ''Mechanical equivalence of heat'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/heat.html#c3</ref> The water increased in [[temperature]], much like it would when put over a flame. This showed that the downward motion of the masses which caused the water to be stirred - a form of mechanical motion - could in fact be equated to an increase in water temperature - or an increase in the heat,

This idea of work and heat equivalence is stated in the [[First law of thermodynamics]], which says that the change in internal energy of a system is the sum of the work done and the heat added to any system. From this, if a system is observed at any state, it is impossible to tell whether it reached this state from an input of work, an input of heat, or a combination of the two.<ref>M. Zemansky, ''The Use and Misuse of the Word "Heat" in Physics Teaching'' [PDF], Available: https://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0CCcQFjAB&url=http%3A%2F%2Fsciphy.tistory.com%2Fattachment%2Fcfile24.uf%401810D1264C95C1266B5C98.pdf&ei=echHVfSeB8TFogT2zYD4DA&usg=AFQjCNEuSqEa3mSsrbe8BadaguDYUmL0RQ&sig2=bSEKcMTJ8bPm5nyHUCciCg&bvm=bv.92291466,d.cGU</ref> This is shown in Figure 2 below.

[[File:Equivalence of heat.gif|center|600px|thumbnail|Figure 2: It is impossible to distinguish between work and heat when observing the final state of a system<ref>Hyperphysics, ''Heat and Work Example'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/heat.html#c2</ref>]]

==References==
{{reflist}}
[[Category:Uploaded]]