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Scientific Methods &
Models of Science and Technology
Development and Its Applications
KPST, 2020
Dr. Ir. ERNA SRI SUGESTI, M.Sc.
School of Electrical Engineering
Telkom University
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Heat and the Second Law of
Thermodynamics
Chapter 4
Great Idea:
Heat is a form of energy that flows from warmer to cooler
objects
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Chapter Outline
Nature’s Direction
Coming to Terms with
HeatHeat Transfer
The Second Law of
Thermodynamics
Consequences of the Second
Law
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NATURE’S DIRECTION
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Nature’s Direction
- First Law of Thermodynamics
- Tendency for disorder
- Evolution to a more probable state
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COMING TO TERMS WITH HEAT
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Heat and Temperature
➢ Heat
⁻ Energy in motion⁻ Warm to cool
➢ Temperature
⁻ Atomic movement
➢ Temperature
⁻ Fahernheit scale⁻ Celsius⁻ Kelvin
• Absolute zero7School of Electrical Engineering
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Temperature Conversions
➢ Conversion to Fahrenheit:
⁻ °F=(1.8 x °C) +32
➢Conversion to Celsius:
⁻ °C=(°F-32)/1.8
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Specific Heat Capacity
▪ Specific heat capacity:
⁻ Quantity of heat needed to raise 1g of a substance by 1 °C
⁻ Highest specific heat
⁻ 1 cal/g °C
▪ Water
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HEAT TRANSFER
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Heat Transfer
➢ Conduction
⁻ Movement of heat by atomic-scale collision
⁻ Thermal conductivity
➢ Convection
⁻ Bulk transfer of molecules⁻ Convection cell
➢ Radiation
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THE SECOND LAW OF
THERMODYNAMICS
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The Second Law of Thermodynamics
3 Statements of the Law :
- Heat does not flow spontaneously from cold to hot
- No engine can exclusively convert heat to work
- Every isolated system tends toward disorder
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Heat Will Not Flow Spontaneously
from a Cold to a Hot Body
➢ Molecular Level
- Faster object shares energy
➢Energy Required
- To cool an object requires energy
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You Cannot Construct an Engine that
Does Nothing but Convert
Heat to Useful Work• Efficiency
• High- to Low-temperature reservoirs
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Every Isolated System Becomes
More Disordered with Time
➢Ordered System
- Regular predictable pattern
➢Disordered System
- Random
➢ Entropy
- Measure of disorder
- The entropy of an isolated
system remains constant or
increases16School of Electrical Engineering
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CONSEQUENCES OF THE
SECOND LAW
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The Arrow of Time
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➢ Four dimensions
- 3 have no directionality
- The 4th has direction
➢ Time
- Second law and time
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Built-in Limitations
of the Universe
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- Some things
cannot happen
- Fossil fuels - Hierarchy of energy
The Second Law’s Consequences
School of Electrical Engineering