Systems 3. Feedbacks Coffee System Tc TRTR The hotter the coffee is The faster it cools Tc-T R...
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Transcript of Systems 3. Feedbacks Coffee System Tc TRTR The hotter the coffee is The faster it cools Tc-T R...
Systems 3
Feedbacks
Coffee System
Tc
TR
The hotter the coffee isThe faster it cools
Tc-TRCooling Rate
The higher the cooling rateThe colder the coffee
Cooling Rate Tc-TR
+
-
Coffee System
Tc
TR
The hotter the coffee isThe faster it cools
Tc-TRCooling Rate
The higher the cooling rateThe colder the coffee
-
+ - = -
Negative connection
The higher the cooling rateThe colder the coffee
Cooling Rate Tc-TR
-Tc
TR
Positive connection
The hotter the coffee isThe faster it cools
Tc-TRCooling Rate+
Tc
TR
Negative feedback loop
Tc
TR
The hotter the coffee isThe faster it cools
Tc-TRCooling Rate
The higher the cooling rateThe colder the coffee
-
+ - = -
Cools with a characteristic time constant, minutes
Classic Positive Feedback
Positive Feedback
Thermostat
Domestic trouble ??
A husband and wife have an electric blanket that has his and her controls. The husband likes it warm and the wife likes it cold.
It’s a very cold night out.
What type feedback is it when they have the wrong controls?
A husband and wife have an electric blanket that has his and her controls. The husband likes it warm and the wife likes it cold.
It’s a very cold night out.
What type feedback is it when they have the wrong controls?
A “positive” feedback loop
Domestic trouble ??
A husband and wife have an electric blanket that has his and her controls. The husband like it warm and the wife likes it cold.
It’s a very cold night out.
What type feedback is it when they have the correct controls?
A husband and wife have an electric blanket that has his and her controls. The husband like it warm and the wife likes it cold.
It’s a very cold night out.
What type feedback is it when they have the correct controls?
Two separate negative feedback loops.
Equilibrium
Stable equilibrium (negative feedback)
Unstable equilibrium (positive feedback)
• ,
PerturbationsSmall changes that disturb a system from its equilibrium state.
Hot Plate Hot Plate
A simple Earth
Heating rate
TE
A simple Earth
Heating rate
TE
Albedo
Absorbed solar
Complete the system diagram
A simple Earth
Heating rate
TE
Albedo
Absorbed solar
Complete the system diagram
+
-
Daisy World
Ave
rage
sur
face
Tem
p
Daisy coverage
TsDaisies
TsDaisies Albedo
Daisy World
Average surface Temp
Ts Daisies
Dai
sy c
over
age Ts Daisies
Daisy World
Average surface Temp
Ts DaisiesD
aisy
cov
erag
e Ts Daisies
albedo
P1
P1
Ts Daisies
albedoP2
P2
