The Energy Balance for Closed Systems

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The Energy Balance for Closed Systems

• The First Law
• and Heat

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Definition of heat...
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The First Law
The adiabatic work done on a closed system is
independent of path for two given states.
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Heat The result of non-adiabatic processes
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Heat defined
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Heat defined
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Energy balances...
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Energy Balances
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Example 1
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Example 1
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Example 2
Heat Loss from from Motor
System Boundary
Mechanical Work to Raise the Mass, m
Battery has stored energy. It is released via
electrical current.
Force mg
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Example 2
For transient operation, chemical energy stored
in the battery is converted to electrical power
and to mechanical work and heat.
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Example 3
Q5
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Example 4
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Cyclic processes...
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Cyclic Processes
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Equivalence of heat and work
This is an important result that says the cyclic
heat and work are the same. It establishes that
heat and work are different forms of energy.
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Key concepts and terms

• Adiabatic Process
• Cycle
• Cyclic Heat
• Cyclic Work
• Energy
• Heat
• Heat Transfer
• Internal Energy