Topic 8: Energy & the Price We Pay
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Transcript of Topic 8: Energy & the Price We Pay
What is Work?
Work is done when a Force acts through a Distance in the direction of the Force
Work = Force x Distance
4 Fundamental forms of Energy:
1 Potential Energy (PE)
2 Kinetic Energy (KE)
3 Electro-Magnetic Energy (E-M)
4 Mass Energy
1 Potential Energy (PE) = “energy of position”
Energy gained by pulling something away from an attractive force
or
Energy gained by pushing something toward a repulsive force
1 Potential Energy (PE) = “energy of position”
Gravitational PE = work done to lift something against attraction of gravity
Gravitational PE gained = weight x height lifted = mg x h
1 Potential Energy (PE) = “energy of position”
Elastic PE = stretching a spring or a rubber band or compressing a spring or a gas or bending a springy bow
1 Potential Energy (PE) = “energy of position”
Electrical PE = pulling + away from –
pushing + toward + or – toward –
1 Potential Energy (PE) = “energy of position”
Electrical PE = pulling + away from –
pushing + toward + or – toward –
First Law of Thermodynamics
“Conservation of Energy”
Energy can neither be created nor destroyed
The amount of Energy in an “isolated system” is constant over time
An isolated system is one where neither matter nor energy can cross between the system and the surroundings.
The whole universe itself is an isolated system, as there are no surroundings to exchange matter or energy with.
An isolated system is one where neither matter nor energy can cross between the system and the surroundings.
The whole universe itself is an isolated system, as there are no surroundings to exchange matter or energy with.
Energy can be transferred (moved) from one place to another
and
Transformed from one form to another
Internal energy
A closed system is one where energy can cross the boundary, but matter cannot.
The internal energy of a closed system changes with heat transfer and work done
Second Law of Thermodynamics
The Entropy of the Universe can only increase (or stay the same) over time.
It cannot ever decrease.
Entropy = disorder = randomness
Second Law of Thermodynamics
The Entropy of the Universe can only increase (or stay the same) over time.
It cannot ever decrease.
Entropy = disorder = randomness
All “changes” that can actually occur result in an increase in the Entropy of the Universe
Entropy is “Time’s Arrow” which points in the direction of “spontaneous” changes = changes that can happen
TemperatureTemperature- a measure of the average kinetic energy of the
molecules making up a substance.
HeatHeat- energy of molecules that is gained/lost through a temperature
difference.