Vincent Selhorst-Jones

Thermodynamics

Slide Duration:

Section 1: Motion
Math Review

16m 49s

Intro
0:00
The Metric System
0:26
Distance, Mass, Volume, and Time
0:27
Scientific Notation
1:40
Examples: 47,000,000,000 and 0.00000002
1:41
Significant Figures
3:18
Significant Figures Overview
3:19
Properties of Significant Figures
4:04
How Significant Figures Interact
7:00
Trigonometry Review
8:57
Pythagorean Theorem, sine, cosine, and tangent
8:58
Inverse Trigonometric Functions
9:48
Inverse Trigonometric Functions
9:49
Vectors
10:44
Vectors
10:45
Scalars
12:10
Scalars
12:11
Breaking a Vector into Components
13:17
Breaking a Vector into Components
13:18
Length of a Vector
13:58
Length of a Vector
13:59
Relationship Between Length, Angle, and Coordinates
14:45
One Dimensional Kinematics

26m 2s

Intro
0:00
Position
0:06
Definition and Example of Position
0:07
Distance
1:11
Definition and Example of Distance
1:12
Displacement
1:34
Definition and Example of Displacement
1:35
Comparison
2:45
Distance vs. Displacement
2:46
Notation
2:54
Notation for Location, Distance, and Displacement
2:55
Speed
3:32
Definition and Formula for Speed
3:33
Example: Speed
3:51
Velocity
4:23
Definition and Formula for Velocity
4:24
∆ - Greek: 'Delta'
5:01
∆ or 'Change In'
5:02
Acceleration
6:02
Definition and Formula for Acceleration
6:03
Example: Acceleration
6:38
Gravity
7:31
Gravity
7:32
Formulas
8:44
Kinematics Formula 1
8:45
Kinematics Formula 2
9:32
Definitional Formulas
14:00
Example 1: Speed of a Rock Being Thrown
14:12
Example 2: How Long Does It Take for the Rock to Hit the Ground?
15:37
Example 3: Acceleration of a Biker
21:09
Example 4: Velocity and Displacement of a UFO
22:43
Multi-Dimensional Kinematics

29m 59s

Intro
0:00
0:07
Scalars and Vectors
0:08
A Note on Vectors
2:12
Indicating Vectors
2:13
Position
3:03
Position
3:04
Distance and Displacement
3:35
Distance and Displacement: Definitions
3:36
Distance and Displacement: Example
4:39
Speed and Velocity
8:57
Speed and Velocity: Definition & Formulas
8:58
Speed and Velocity: Example
10:06
Speed from Velocity
12:01
Speed from Velocity
12:02
Acceleration
14:09
Acceleration
14:10
Gravity
14:26
Gravity
14:27
Formulas
15:11
Formulas with Vectors
15:12
Example 1: Average Acceleration
16:57
Example 2A: Initial Velocity
19:14
Example 2B: How Long Does It Take for the Ball to Hit the Ground?
21:35
Example 2C: Displacement
26:46
Frames of Reference

18m 36s

Intro
0:00
Fundamental Example
0:25
Fundamental Example Part 1
0:26
Fundamental Example Part 2
1:20
General Case
2:36
Particle P and Two Observers A and B
2:37
Speed of P from A's Frame of Reference
3:05
3:22
Acceleration Shows the Change in Velocity
3:23
Acceleration when Velocity is Constant
3:48
Multi-Dimensional Case
4:35
Multi-Dimensional Case
4:36
Some Notes
5:04
Choosing the Frame of Reference
5:05
Example 1: What Velocity does the Ball have from the Frame of Reference of a Stationary Observer?
7:27
Example 2: Velocity, Speed, and Displacement
9:26
Example 3: Speed and Acceleration in the Reference Frame
12:44
Uniform Circular Motion

16m 34s

Intro
0:00
Centripetal Acceleration
1:21
Centripetal Acceleration of a Rock Being Twirled Around on a String
1:22
Looking Closer: Instantaneous Velocity and Tangential Velocity
2:35
Magnitude of Acceleration
3:55
Centripetal Acceleration Formula
5:14
You Say You Want a Revolution
6:11
What is a Revolution?
6:12
How Long Does it Take to Complete One Revolution Around the Circle?
6:51
Example 1: Centripetal Acceleration of a Rock
7:40
Example 2: Magnitude of a Car's Acceleration While Turning
9:20
Example 3: Speed of a Point on the Edge of a US Quarter
13:10
Section 2: Force
Newton's 1st Law

12m 37s

Intro
0:00
Newton's First Law/ Law of Inertia
2:45
A Body's Velocity Remains Constant Unless Acted Upon by a Force
2:46
Mass & Inertia
4:07
Mass & Inertia
4:08
Mass & Volume
5:49
Mass & Volume
5:50
Mass & Weight
7:08
Mass & Weight
7:09
Example 1: The Speed of a Rocket
8:47
Example 2: Which of the Following Has More Inertia?
10:06
Example 3: Change in Inertia
11:51
Newton's 2nd Law: Introduction

27m 5s

Intro
0:00
Net Force
1:42
Consider a Block That is Pushed On Equally From Both Sides
1:43
What if One of the Forces was Greater Than the Other?
2:29
The Net Force is All the Forces Put Together
2:43
Newton's Second Law
3:14
Net Force = (Mass) x (Acceleration)
3:15
Units
3:48
The Units of Newton's Second Law
3:49
Free-Body Diagram
5:34
Free-Body Diagram
5:35
Special Forces: Gravity (Weight)
8:05
Force of Gravity
8:06
Special Forces: Normal Force
9:22
Normal Force
9:23
Special Forces: Tension
10:34
Tension
10:35
Example 1: Force and Acceleration
12:19
Example 2: A 5kg Block is Pushed by Five Forces
13:24
Example 3: A 10kg Block Resting On a Table is Tethered Over a Pulley to a Free-Hanging 2kg Block
16:30
Newton's 2nd Law: Multiple Dimensions

27m 47s

Intro
0:00
Newton's 2nd Law in Multiple Dimensions
0:12
Newton's 2nd Law in Multiple Dimensions
0:13
Components
0:52
Components
0:53
Example: Force in Component Form
1:02
Special Forces
2:39
Review of Special Forces: Gravity, Normal Force, and Tension
2:40
Normal Forces
3:35
Why Do We Call It the Normal Forces?
3:36
Normal Forces on a Flat Horizontal and Vertical Surface
5:00
Normal Forces on an Incline
6:05
Example 1: A 5kg Block is Pushed By a Force of 3N to the North and a Force of 4N to the East
10:22
Example 2: A 20kg Block is On an Incline of 50° With a Rope Holding It In Place
16:08
Example 3: A 10kg Block is On an Incline of 20° Attached By Rope to a Free-hanging Block of 5kg
20:50

42m 5s

Intro
0:00
Block and Tackle Pulley System
0:30
A Single Pulley Lifting System
0:31
A Double Pulley Lifting System
1:32
2:59
Example 1: A Free-hanging, Massless String is Holding Up Three Objects of Unknown Mass
4:40
Example 2: An Object is Acted Upon by Three Forces
10:23
Example 3: A Chandelier is Suspended by a Cable From the Roof of an Elevator
17:13
Example 4: A 20kg Baboon Climbs a Massless Rope That is Attached to a 22kg Crate
23:46
Example 5: Two Blocks are Roped Together on Inclines of Different Angles
33:17
Newton's Third Law

16m 47s

Intro
0:00
Newton's Third Law
0:50
Newton's Third Law
0:51
Everyday Examples
1:24
Hammer Hitting a Nail
1:25
Swimming
2:08
Car Driving
2:35
Walking
3:15
Note
3:57
Newton's Third Law Sometimes Doesn't Come Into Play When Solving Problems: Reason 1
3:58
Newton's Third Law Sometimes Doesn't Come Into Play When Solving Problems: Reason 2
5:36
Example 1: What Force Does the Moon Pull on Earth?
7:04
Example 2: An Astronaut in Deep Space Throwing a Wrench
8:38
Example 3: A Woman Sitting in a Bosun's Chair that is Hanging from a Rope that Runs Over a Frictionless Pulley
12:51
Friction

50m 11s

Intro
0:00
Introduction
0:04
Our Intuition - Materials
0:30
Our Intuition - Weight
2:48
Our Intuition - Normal Force
3:45
The Normal Force and Friction
4:11
Two Scenarios: Same Object, Same Surface, Different Orientations
4:12
6:36
Friction as an Equation
7:23
Summing Up Friction
7:24
Friction as an Equation
7:36
The Direction of Friction
10:33
The Direction of Friction
10:34
A Quick Example
11:16
Which Block Will Accelerate Faster?
11:17
Static vs. Kinetic
14:52
Static vs. Kinetic
14:53
Static and Kinetic Coefficient of Friction
16:31
How to Use Static Friction
17:40
How to Use Static Friction
17:41
Some Examples of μs and μk
19:51
Some Examples of μs and μk
19:52
A Remark on Wheels
22:19
A Remark on Wheels
22:20
Example 1: Calculating μs and μk
28:02
Example 2: At What Angle Does the Block Begin to Slide?
31:35
Example 3: A Block is Against a Wall, Sliding Down
36:30
Example 4: Two Blocks Sitting Atop Each Other
40:16
Force & Uniform Circular Motion

26m 45s

Intro
0:00
Centripetal Force
0:46
Equations for Centripetal Force
0:47
Centripetal Force in Action
1:26
Where Does Centripetal Force Come From?
2:39
Where Does Centripetal Force Come From?
2:40
Centrifugal Force
4:05
Centrifugal Force Part 1
4:06
Centrifugal Force Part 2
6:16
Example 1: Part A - Centripetal Force On the Car
8:12
Example 1: Part B - Maximum Speed the Car Can Take the Turn At Without Slipping
8:56
Example 2: A Bucket Full of Water is Spun Around in a Vertical Circle
15:13
Example 3: A Rock is Spun Around in a Vertical Circle
21:36
Section 3: Energy
Work

28m 34s

Intro
0:00
Equivocation
0:05
Equivocation
0:06
Introduction to Work
0:32
Scenarios: 10kg Block on a Frictionless Table
0:33
Scenario: 2 Block of Different Masses
2:52
Work
4:12
Work and Force
4:13
Paralleled vs. Perpendicular
4:46
Work: A Formal Definition
7:33
An Alternate Formula
9:00
An Alternate Formula
9:01
Units
10:40
Unit for Work: Joule (J)
10:41
Example 1: Calculating Work of Force
11:32
Example 2: Work and the Force of Gravity
12:48
Example 3: A Moving Box & Force Pushing in the Opposite Direction
15:11
Example 4: Work and Forces with Directions
18:06
Example 5: Work and the Force of Gravity
23:16
Energy: Kinetic

39m 7s

Intro
0:00
Types of Energy
0:04
Types of Energy
0:05
Conservation of Energy
1:12
Conservation of Energy
1:13
What is Energy?
4:23
Energy
4:24
What is Work?
5:01
Work
5:02
Circular Definition, Much?
5:46
Circular Definition, Much?
5:47
Derivation of Kinetic Energy (Simplified)
7:44
Simplified Picture of Work
7:45
Consider the Following Three Formulas
8:42
Kinetic Energy Formula
11:01
Kinetic Energy Formula
11:02
Units
11:54
Units for Kinetic Energy
11:55
Conservation of Energy
13:24
Energy Cannot be Made or Destroyed, Only Transferred
13:25
Friction
15:02
How Does Friction Work?
15:03
Example 1: Velocity of a Block
15:59
Example 2: Energy Released During a Collision
18:28
Example 3: Speed of a Block
22:22
Example 4: Speed and Position of a Block
26:22
Energy: Gravitational Potential

28m 10s

Intro
0:00
Why Is It Called Potential Energy?
0:21
Why Is It Called Potential Energy?
0:22
Introduction to Gravitational Potential Energy
1:20
Consider an Object Dropped from Ever-Increasing heights
1:21
Gravitational Potential Energy
2:02
Gravitational Potential Energy: Derivation
2:03
Gravitational Potential Energy: Formulas
2:52
Gravitational Potential Energy: Notes
3:48
Conservation of Energy
5:50
Conservation of Energy and Formula
5:51
Example 1: Speed of a Falling Rock
6:31
Example 2: Energy Lost to Air Drag
10:58
Example 3: Distance of a Sliding Block
15:51
Example 4: Swinging Acrobat
21:32
Energy: Elastic Potential

44m 16s

Intro
0:00
Introduction to Elastic Potential
0:12
Elastic Object
0:13
Spring Example
1:11
Hooke's Law
3:27
Hooke's Law
3:28
Example of Hooke's Law
5:14
Elastic Potential Energy Formula
8:27
Elastic Potential Energy Formula
8:28
Conservation of Energy
10:17
Conservation of Energy
10:18
You Ain't Seen Nothin' Yet
12:12
You Ain't Seen Nothin' Yet
12:13
Example 1: Spring-Launcher
13:10
Example 2: Compressed Spring
18:34
Example 3: A Block Dangling From a Massless Spring
24:33
Example 4: Finding the Spring Constant
36:13
Power & Simple Machines

28m 54s

Intro
0:00
Introduction to Power & Simple Machines
0:06
What's the Difference Between a Go-Kart, a Family Van, and a Racecar?
0:07
Consider the Idea of Climbing a Flight of Stairs
1:13
Power
2:35
P= W / t
2:36
Alternate Formulas
2:59
Alternate Formulas
3:00
Units
4:24
Units for Power: Watt, Horsepower, and Kilowatt-hour
4:25
Block and Tackle, Redux
5:29
Block and Tackle Systems
5:30
Machines in General
9:44
Levers
9:45
Ramps
10:51
Example 1: Power of Force
12:22
Example 2: Power &Lifting a Watermelon
14:21
Example 3: Work and Instantaneous Power
16:05
Example 4: Power and Acceleration of a Race car
25:56
Section 4: Momentum
Center of Mass

36m 55s

Intro
0:00
Introduction to Center of Mass
0:04
Consider a Ball Tossed in the Air
0:05
Center of Mass
1:27
Definition of Center of Mass
1:28
Example of center of Mass
2:13
Center of Mass: Derivation
4:21
Center of Mass: Formula
6:44
Center of Mass: Formula, Multiple Dimensions
8:15
Center of Mass: Symmetry
9:07
Center of Mass: Non-Homogeneous
11:00
Center of Gravity
12:09
Center of Mass vs. Center of Gravity
12:10
Newton's Second Law and the Center of Mass
14:35
Newton's Second Law and the Center of Mass
14:36
Example 1: Finding The Center of Mass
16:29
Example 2: Finding The Center of Mass
18:55
Example 3: Finding The Center of Mass
21:46
Example 4: A Boy and His Mail
28:31
Linear Momentum

22m 50s

Intro
0:00
Introduction to Linear Momentum
0:04
Linear Momentum Overview
0:05
Consider the Scenarios
0:45
Linear Momentum
1:45
Definition of Linear Momentum
1:46
Impulse
3:10
Impulse
3:11
Relationship Between Impulse & Momentum
4:27
Relationship Between Impulse & Momentum
4:28
Why is It Linear Momentum?
6:55
Why is It Linear Momentum?
6:56
Example 1: Momentum of a Skateboard
8:25
Example 2: Impulse and Final Velocity
8:57
Example 3: Change in Linear Momentum and magnitude of the Impulse
13:53
Example 4: A Ball of Putty
17:07
Collisions & Linear Momentum

40m 55s

Intro
0:00
Investigating Collisions
0:45
Momentum
0:46
Center of Mass
1:26
Derivation
1:56
Extending Idea of Momentum to a System
1:57
Impulse
5:10
Conservation of Linear Momentum
6:14
Conservation of Linear Momentum
6:15
Conservation and External Forces
7:56
Conservation and External Forces
7:57
Momentum Vs. Energy
9:52
Momentum Vs. Energy
9:53
Types of Collisions
12:33
Elastic
12:34
Inelastic
12:54
Completely Inelastic
13:24
Everyday Collisions and Atomic Collisions
13:42
Example 1: Impact of Two Cars
14:07
Example 2: Billiard Balls
16:59
Example 3: Elastic Collision
23:52
Example 4: Bullet's Velocity
33:35
Section 5: Gravity
Gravity & Orbits

34m 53s

Intro
0:00
Law of Universal Gravitation
1:39
Law of Universal Gravitation
1:40
Force of Gravity Equation
2:14
Gravitational Field
5:38
Gravitational Field Overview
5:39
Gravitational Field Equation
6:32
Orbits
9:25
Orbits
9:26
The 'Falling' Moon
12:58
The 'Falling' Moon
12:59
Example 1: Force of Gravity
17:05
Example 2: Gravitational Field on the Surface of Earth
20:35
Example 3: Orbits
23:15
Example 4: Neutron Star
28:38
Section 6: Waves
Intro to Waves

35m 35s

Intro
0:00
Pulse
1:00
Introduction to Pulse
1:01
Wave
1:59
Wave Overview
2:00
Wave Types
3:16
Mechanical Waves
3:17
Electromagnetic Waves
4:01
Matter or Quantum Mechanical Waves
4:43
Transverse Waves
5:12
Longitudinal Waves
6:24
Wave Characteristics
7:24
Amplitude and Wavelength
7:25
Wave Speed (v)
10:13
Period (T)
11:02
Frequency (f)
12:33
v = λf
14:51
Wave Equation
16:15
Wave Equation
16:16
Angular Wave Number
17:34
Angular Frequency
19:36
Example 1: CPU Frequency
24:35
Example 2: Speed of Light, Wavelength, and Frequency
26:11
Example 3: Spacing of Grooves
28:35
Example 4: Wave Diagram
31:21
Waves, Cont.

52m 57s

Intro
0:00
Superposition
0:38
Superposition
0:39
Interference
1:31
Interference
1:32
Visual Example: Two Positive Pulses
2:33
Visual Example: Wave
4:02
Phase of Cycle
6:25
Phase Shift
7:31
Phase Shift
7:32
Standing Waves
9:59
Introduction to Standing Waves
10:00
Visual Examples: Standing Waves, Node, and Antinode
11:27
Standing Waves and Wavelengths
15:37
Standing Waves and Resonant Frequency
19:18
Doppler Effect
20:36
When Emitter and Receiver are Still
20:37
When Emitter is Moving Towards You
22:31
When Emitter is Moving Away
24:12
Doppler Effect: Formula
25:58
Example 1: Superposed Waves
30:00
Example 2: Superposed and Fully Destructive Interference
35:57
Example 3: Standing Waves on a String
40:45
Example 4: Police Siren
43:26
Example Sounds: 800 Hz, 906.7 Hz, 715.8 Hz, and Slide 906.7 to 715.8 Hz
48:49
Sound

36m 24s

Intro
0:00
Speed of Sound
1:26
Speed of Sound
1:27
Pitch
2:44
High Pitch & Low Pitch
2:45
Normal Hearing
3:45
Infrasonic and Ultrasonic
4:02
Intensity
4:54
Intensity: I = P/A
4:55
Intensity of Sound as an Outwardly Radiating Sphere
6:32
Decibels
9:09
Human Threshold for Hearing
9:10
Decibel (dB)
10:28
Sound Level β
11:53
Loudness Examples
13:44
Loudness Examples
13:45
Beats
15:41
Beats & Frequency
15:42
Audio Examples of Beats
17:04
Sonic Boom
20:21
Sonic Boom
20:22
Example 1: Firework
23:14
Example 2: Intensity and Decibels
24:48
Example 3: Decibels
28:24
Example 4: Frequency of a Violin
34:48
Light

19m 38s

Intro
0:00
The Speed of Light
0:31
Speed of Light in a Vacuum
0:32
Unique Properties of Light
1:20
Lightspeed!
3:24
Lightyear
3:25
Medium
4:34
Light & Medium
4:35
Electromagnetic Spectrum
5:49
Electromagnetic Spectrum Overview
5:50
Electromagnetic Wave Classifications
7:05
7:06
Microwave
8:30
Infrared and Visible Spectrum
9:02
Ultraviolet, X-rays, and Gamma Rays
9:33
So Much Left to Explore
11:07
So Much Left to Explore
11:08
Example 1: How Much Distance is in a Light-year?
13:16
Example 2: Electromagnetic Wave
16:50
Example 3: Radio Station & Wavelength
17:55
Section 7: Thermodynamics
Fluids

42m 52s

Intro
0:00
Fluid?
0:48
What Does It Mean to be a Fluid?
0:49
Density
1:46
What is Density?
1:47
Formula for Density: ρ = m/V
2:25
Pressure
3:40
Consider Two Equal Height Cylinders of Water with Different Areas
3:41
Definition and Formula for Pressure: p = F/A
5:20
Pressure at Depth
7:02
Pressure at Depth Overview
7:03
Free Body Diagram for Pressure in a Container of Fluid
8:31
Equations for Pressure at Depth
10:29
Absolute Pressure vs. Gauge Pressure
12:31
Absolute Pressure vs. Gauge Pressure
12:32
Why Does Gauge Pressure Matter?
13:51
Depth, Not Shape or Direction
15:22
Depth, Not Shape or Direction
15:23
Depth = Height
18:27
Depth = Height
18:28
Buoyancy
19:44
Buoyancy and the Buoyant Force
19:45
Archimedes' Principle
21:09
Archimedes' Principle
21:10
22:30
22:31
Example 1: Rock & Fluid
23:47
Example 2: Pressure of Water at the Top of the Reservoir
28:01
Example 3: Wood & Fluid
31:47
Example 4: Force of Air Inside a Cylinder
36:20
Intro to Temperature & Heat

34m 6s

Intro
0:00
Absolute Zero
1:50
Absolute Zero
1:51
Kelvin
2:25
Kelvin
2:26
Heat vs. Temperature
4:21
Heat vs. Temperature
4:22
Heating Water
5:32
Heating Water
5:33
Specific Heat
7:44
Specific Heat: Q = cm(∆T)
7:45
Heat Transfer
9:20
Conduction
9:24
Convection
10:26
11:35
Example 1: Converting Temperature
13:21
Example 2: Calories
14:54
Example 3: Thermal Energy
19:00
Example 4: Temperature When Mixture Comes to Equilibrium Part 1
20:45
Example 4: Temperature When Mixture Comes to Equilibrium Part 2
24:55
Change Due to Heat

44m 3s

Intro
0:00
Linear Expansion
1:06
Linear Expansion: ∆L = Lα(∆T)
1:07
Volume Expansion
2:34
Volume Expansion: ∆V = Vβ(∆T)
2:35
Gas Expansion
3:40
Gas Expansion
3:41
The Mole
5:43
Conceptual Example
5:44
7:30
Ideal Gas Law
9:22
Ideal Gas Law: pV = nRT
9:23
p = Pressure of the Gas
10:07
V = Volume of the Gas
10:34
n = Number of Moles of Gas
10:44
R = Gas Constant
10:58
T = Temperature
11:58
A Note On Water
12:21
A Note On Water
12:22
Change of Phase
15:55
Change of Phase
15:56
Change of Phase and Pressure
17:31
Phase Diagram
18:41
Heat of Transformation
20:38
Heat of Transformation: Q = Lm
20:39
Example 1: Linear Expansion
22:38
Example 2: Explore Why β = 3α
24:40
Example 3: Ideal Gas Law
31:38
Example 4: Heat of Transformation
38:03
Thermodynamics

27m 30s

Intro
0:00
First Law of Thermodynamics
1:11
First Law of Thermodynamics
1:12
Engines
2:25
Conceptual Example: Consider a Piston
2:26
Second Law of Thermodynamics
4:17
Second Law of Thermodynamics
4:18
Entropy
6:09
Definition of Entropy
6:10
Conceptual Example of Entropy: Stick of Dynamite
7:00
Order to Disorder
8:22
Order and Disorder in a System
8:23
The Poets Got It Right
10:20
The Poets Got It Right
10:21
Engines in General
11:21
Engines in General
11:22
Efficiency
12:06
Measuring the Efficiency of a System
12:07
Carnot Engine ( A Limit to Efficiency)
13:20
Carnot Engine & Maximum Possible Efficiency
13:21
Example 1: Internal Energy
15:15
Example 2: Efficiency
16:13
Example 3: Second Law of Thermodynamics
17:05
Example 4: Maximum Efficiency
20:10
Section 8: Electricity
Electric Force & Charge

41m 35s

Intro
0:00
Charge
1:04
Overview of Charge
1:05
Positive and Negative Charges
1:19
A Simple Model of the Atom
2:47
Protons, Electrons, and Neutrons
2:48
Conservation of Charge
4:47
Conservation of Charge
4:48
Elementary Charge
5:41
Elementary Charge and the Unit Coulomb
5:42
Coulomb's Law
8:29
Coulomb's Law & the Electrostatic Force
8:30
Coulomb's Law Breakdown
9:30
Conductors and Insulators
11:11
Conductors
11:12
Insulators
12:31
Conduction
15:08
Conduction
15:09
Conceptual Examples
15:58
Induction
17:02
Induction Overview
17:01
Conceptual Examples
18:18
Example 1: Electroscope
20:08
Example 2: Positive, Negative, and Net Charge of Iron
22:15
Example 3: Charge and Mass
27:52
Example 4: Two Metal Spheres
31:58
Electric Fields & Potential

34m 44s

Intro
0:00
Electric Fields
0:53
Electric Fields Overview
0:54
Size of q2 (Second Charge)
1:34
Size of q1 (First Charge)
1:53
Electric Field Strength: Newtons Per Coulomb
2:55
Electric Field Lines
4:19
Electric Field Lines
4:20
Conceptual Example 1
5:17
Conceptual Example 2
6:20
Conceptual Example 3
6:59
Conceptual Example 4
7:28
8:47
8:48
Why Does It Work?
9:33
Electric Potential Energy
11:40
Electric Potential Energy
11:41
Electric Potential
13:44
Electric Potential
13:45
Difference Between Two States
14:29
Electric Potential is Measured in Volts
15:12
Ground Voltage
16:09
Potential Differences and Reference Voltage
16:10
Ground Voltage
17:20
Electron-volt
19:17
Electron-volt
19:18
Equipotential Surfaces
20:29
Equipotential Surfaces
20:30
Equipotential Lines
21:21
Equipotential Lines
21:22
Example 1: Electric Field
22:40
Example 2: Change in Energy
24:25
Example 3: Constant Electrical Field
27:06
Example 4: Electrical Field and Change in Voltage
29:06
Example 5: Voltage and Energy
32:14
Electric Current

29m 12s

Intro
0:00
Electric Current
0:31
Electric Current
0:32
Amperes
1:27
Moving Charge
1:52
Conceptual Example: Electric Field and a Conductor
1:53
Voltage
3:26
Resistance
5:05
Given Some Voltage, How Much Current Will Flow?
5:06
Resistance: Definition and Formula
5:40
Resistivity
7:31
Resistivity
7:32
Resistance for a Uniform Object
9:31
Energy and Power
9:55
How Much Energy Does It take to Move These Charges Around?
9:56
What Do We Call Energy Per Unit Time?
11:08
Formulas to Express Electrical Power
11:53
Voltage Source
13:38
Introduction to Voltage Source
13:39
Obtaining a Voltage Source: Generator
15:15
Obtaining a Voltage Source: Battery
16:19
Speed of Electricity
17:17
Speed of Electricity
17:18
Example 1: Electric Current & Moving Charge
19:40
Example 2: Electric Current & Resistance
20:31
Example 3: Resistivity & Resistance
21:56
Example 4: Light Bulb
25:16
Electric Circuits

52m 2s

Intro
0:00
Electric Circuits
0:51
Current, Voltage, and Circuit
0:52
Resistor
5:05
Definition of Resistor
5:06
Conceptual Example: Lamps
6:18
Other Fundamental Components
7:04
Circuit Diagrams
7:23
Introduction to Circuit Diagrams
7:24
Wire
7:42
Resistor
8:20
Battery
8:45
Power Supply
9:41
Switch
10:02
Wires: Bypass and Connect
10:53
A Special Not in General
12:04
Example: Simple vs. Complex Circuit Diagram
12:45
Kirchoff's Circuit Laws
15:32
Kirchoff's Circuit Law 1: Current Law
15:33
Kirchoff's Circuit Law 1: Visual Example
16:57
Kirchoff's Circuit Law 2: Voltage Law
17:16
Kirchoff's Circuit Law 2: Visual Example
19:23
Resistors in Series
21:48
Resistors in Series
21:49
Resistors in Parallel
23:33
Resistors in Parallel
23:34
Voltmeter and Ammeter
28:35
Voltmeter
28:36
Ammeter
30:05
Direct Current vs. Alternating Current
31:24
Direct Current vs. Alternating Current
31:25
Visual Example: Voltage Graphs
33:29
Example 1: What Voltage is Read by the Voltmeter in This Diagram?
33:57
Example 2: What Current Flows Through the Ammeter When the Switch is Open?
37:42
Example 3: How Much Power is Dissipated by the Highlighted Resistor When the Switch is Open? When Closed?
41:22
Example 4: Design a Hallway Light Switch
45:14
Section 9: Magnetism
Magnetism

25m 47s

Intro
0:00
Magnet
1:27
Magnet Has Two Poles
1:28
Magnetic Field
1:47
Always a Dipole, Never a Monopole
2:22
Always a Dipole, Never a Monopole
2:23
Magnetic Fields and Moving Charge
4:01
Magnetic Fields and Moving Charge
4:02
Magnets on an Atomic Level
4:45
Magnets on an Atomic Level
4:46
Evenly Distributed Motions
5:45
Unevenly Distributed Motions
6:22
Current and Magnetic Fields
9:42
Current Flow and Magnetic Field
9:43
Electromagnet
11:35
Electric Motor
13:11
Electric Motor
13:12
Generator
15:38
A Changing Magnetic Field Induces a Current
15:39
Example 1: What Kind of Magnetic Pole must the Earth's Geographic North Pole Be?
19:34
Example 2: Magnetic Field and Generator/Electric Motor
20:56
Example 3: Destroying the Magnetic Properties of a Permanent Magnet
23:08
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### Thermodynamics

• The first law of thermodynamics states that the amount of heat put into a system is equal to the change in the system's internal energy and the work the system does:
 Q = ∆Einternal + W.
• An engine is a clever way to convert heat into work.
• The second law of thermodynamics states that heat always flows from hot objects to cold objects (unless external work is put in).
• Entropy is a measure of chaos and disorder: how random the exact configuration of a system is.
• We can re-state the second law of thermodynamics as, "For all processes, entropy either increases or remains the same. It never decreases." Why does this mean the same thing? Temperature is random, vibratory motion. If we spread this motion out over more objects, we've spread out the randomness over more possibilities, increasing our total randomness.
• Ordered systems tend to disorder. Systems that increase their own order must do it by causing even greater disorder elsewhere.
• For an engine, efficiency (ε) is a measure of how much work we get out for the heat we put in:
 ε = W Q = energy we get outenergy we put in .
• It is impossible for an engine to have 100% efficiency (i.e., ε = 1.00).
• A Carnot engine is a theoretical engine with the maximum possible efficiency. Its efficiency depends on how hot the heat source is and how cold the the sink/exhaust is:
 εmax, carnot = 1 − TcoldThot .

### Thermodynamics

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

• Intro 0:00
• First Law of Thermodynamics 1:11
• First Law of Thermodynamics
• Engines 2:25
• Conceptual Example: Consider a Piston
• Second Law of Thermodynamics 4:17
• Second Law of Thermodynamics
• Entropy 6:09
• Definition of Entropy
• Conceptual Example of Entropy: Stick of Dynamite
• Order to Disorder 8:22
• Order and Disorder in a System
• The Poets Got It Right 10:20
• The Poets Got It Right
• Engines in General 11:21
• Engines in General
• Efficiency 12:06
• Measuring the Efficiency of a System
• Carnot Engine ( A Limit to Efficiency) 13:20
• Carnot Engine & Maximum Possible Efficiency
• Example 1: Internal Energy 15:15
• Example 2: Efficiency 16:13
• Example 3: Second Law of Thermodynamics 17:05
• Example 4: Maximum Efficiency 20:10

### Transcription: Thermodynamics

Hi welcome to educator.com. Today we’re going to be talking about thermo dynamics.0000

At this point it should be really clear that the study of heat and temperature incredibly important to any kind of science.0005

We’ve talked about how it causes expansion, how it causes changes of phase, how there’s just all this stuff that happens based on the temperature of that substance is at.0011

So it’s going to affect chemistry, it’s going to affect biology; it’s going to affect physics. It really, really matters.0020

If you want to do electrical engineering that’s going to matter. Temperature is incredibly important.0025

It has a huge effect on how things operate and even through some clever arraignment we can start to take advantage of that.0030

We can create a thing an engine. You can use heat to do work. Through engines we’re able to cause heat to be beneficial to us in all sorts of ways.0035

In addition to the fact that we might want say a warm room, so it might be…we’ll be able to understand heat better from being able to get heat into a location or heat out of a location.0046

This study is called thermodynamics and it’s what we’ve been talking about for the past two lessons.0057

In general, thermodynamics is way to study heat and its relationship to energy and work.0061

Let’s take a look at some of the laws that make up thermo dynamics.0068

The first law of thermo dynamics is a slight expansion of conservation of energy. You’ve probably already take it for granted and probably figured this out on your own.0072

We’ve talked about it and we’ve almost certainly had this idea introduced to you for a long time. But we haven’t explicitly stated it before.0081

Let’s put it in words. The amount of heat energy we put into a system is equal to the change in that systems internal energy plus the amount of work this system does.0087

Symbolically we get that q; heat energy is equal to change in internal energy plus work.0097

Now why do we use the words internal energy instead of just temperature?0104

Well internal energy lets us talk about how much energy is in the system. Temperature is a specific measure of the average of the system.0108

If we’ve got a 50 kilogram block of steel versus a drop of water at the same temperature in both of those things it’s going to have different amounts of internal energy.0114

There’s even some other things to consider. We can instead be talking about the pressure and volume of the thing without directly relating to the temperature.0124

We can talk about internal energy as more than something that’s just a function of the temperature.0131

It’s the…how much motion is happening in internally, what’s happening, the vibration of the atoms that make up the substance that we’re talking about.0136

How can we talk about heat doing work? Let’s explore one possible way that heat could do simple work.0147

Heat does work in many ways. If we just have an open flame, it’s going to cause work to happen by making those molecules become more energetic and expand out and push out in all directions so it’s causing work by increasing their speed and moving them around.0154

That’s not a very easy way to think about of it though and its not certainly useful work. Let’s think in terms of an engine.0169

For a simplified example we’ll consider a piston, it’s a cylinder full of air where end can move but the enclosure is fully air tight.0175

What would happen if we heat the air at the bottom of it? If we heat the air down here we’re going to cause that air, remember if we had a single volume and we heated it, we caused increase in temperature, it would cause increase in pressure.0183

So in our piston, when we heat that air we’re going to cause those air molecules to start moving around more. Since they’re moving around more they’ve got more pressure.0197

Since they’ve got more pressure they’re now pushing on that piston plate more which means that they’re actually able to cancel out the force of gravity and able to push past it.0205

They’re going to push out as their volume increases, they’re going to wind up having less pressure and less temperature until more temperature gets in.0214

They’re going to be able sort of…as they become higher in temperature they’ll be able to push out the piston.0220

Pushing out the piston will have a connection to the amount of heat energy that would put in.0226

Some will go into raising the internal energy of the atoms, some of it will go into just actual doing work, actually doing work lifting the piston up.0230

We’ve got a way to be able to talk about how…we have a definite example of heat being able to both raise the internal energy but also at the same time cause work to be done external to just they system of the air and the heat.0240

We’re able to do something outside the system lifting that block.0254

The second law of thermo dynamics is similar to the first law. The second law is one that we’ve haven’t especially talked about it but it’s one that we’re definitely ready to understand.0259

One that is probably even certainly more obvious than the first one, at least the way it’s going to be stated here.0268

One way to put the second law is that without external work heat never flows from a cold object to a hot object.0275

If something's cold it isn’t going to colder to make something else even hotter, that doesn’t make sense.0283

It goes from high to low, is what we’re used to. Heat is in some way something that we think of as water.0289

If you’ve got something hot it pours out until it’s evenly spread out. Hot things go down to cold things but cold things don’t, of their own accord, go to hot things.0295

One possible way to fight this out is…to defeat this is by putting work into the system, that’s what a refrigerator does.0305

There’s a clever way to mechanically cause the heat in the box to be put into something else and have that dissipated somewhere else, but we have to put in external work.0313

Without external interference, heat always goes from hot objects to cold objects.0324

This probably seems shockingly obvious; you’d never drop an ice cube in water and expect the water to get hotter while the ice cube got colder. It’s completely intuitive to this at this point in our lives.0333

Hot things make the things around them hotter. They do not themselves get hotter from being around cold things. They make the cold things hotter and the cold things make hot things colder, simple as that.0344

But this idea has really important ramifications. One way to state this was what we just said, heat never flows too cold to hot.0357

Another way to state it is through the idea of entropy. This idea of entropy is really important.0364

We haven’t discussed entropy is yet but another way to put the second law of thermo dynamics is to say that entropy will either increase or remain the same for any process.0371

For any action for any reaction. Entropy is always going to stay the same or get larger.0380

Almost all the time, it’s going to get larger. Entropy never decreases.0385

What the heck is entropy? Entropy is a measure of disorder or chaos. Virtually any real life process will take something organized and cause it to become less organized.0390

As something becomes less organized, the organized something is the more entropy it has.0400

This idea of entropy can be put into a specific mathematical formula. We can talk about it mathematically. We’re not going to, it’s enough for our purposes right now to just explore it a little bit on the surface and get the idea that entropy means chaos, it means randomness, it means disorder.0405

A good example of this would be if you had a stick of dynamite and you lit it and it blew up.0421

A stick of dynamite starts off as this really tightly packed configuration of very complex molecules. We’ve got the very complex molecules that store all of that chemical energy inside of there.0425

We’ve got them tightly packed into this single orderly piece of dynamite that’s well wrapped up.0438

You light the fuse, so you apply a little bit of heat, the fuse runs in; it manages to apply some heat to the dynamite.0443

The dynamite takes that and has a chain reaction where way more heat is released. Way more heat is released; it manages to cause all of those complex molecules to transform into simpler molecules, which allows that heat to be released.0449

All of that heat and pressure causes the dynamite to blast out. We’ve got a release of heat which means our molecules are now vibrating around, they’re more random, there’s more motion going on.0462

They’re bouncing around, they’re more disordered. We’ve got all of those complex, complicated molecules that have been blow…not blow, been transformed into smaller, simpler forms of molecules.0471

Their transformation from the complex to the simple has released energy. Finally the process of exploding has caused the entire piece of dynamite to be blown over a large area randomly.0485

We’ve got all of this chaos, all of this disorder from lighting this stick of something that started off fairly ordered.0495

In general, order will tend to disorder. Over time ordered systems go to disordered system. Unless they’re perfectly isolated with no ongoing processes.0504

If nothing’s going on inside of them and they’re completely removed from everything else, they’ll be able to stay the same level of entropy.0512

But that’s not possible in the real world. We can’t perfectly insulate something from the world around it and we can’t keep everything from stopping happening inside of it.0519

Whatever we’ve what, whatever it is; it’s going to over time become more and more disordered. More and more entropic, more entropy and it’s going to have more randomness.0527

Over time order falls into disorder. A given system like a living being can increase its own order, but it causes this at a greater increase in disorder elsewhere.0537

While you might be able to lower the entropy in your body by eating a good breakfast and working out, by doing things like that your body is taking care of itself.0548

Its doing things, it’s making a very complex system. But over the course of doing that you have to eat that food, all those complex chemicals in the food are broken down into simpler chemicals, turned into waste products.0556

The air we breathe in it becomes less complex to some extent turning oxygen into carbon dioxide is an interesting question the way it’s working.0567

We’re able to take all of these things around, we produce heat, causing more motion, more randomness. The whole process of being a complex thing, being able to stay complex and not break down yourself means that you have to cause complexness in other things to break down.0575

You have to take complexity from elsewhere and break it down to keep up your own level of complexity.0592

While you’re able to have order in your own body, it causes an even greater increase in disorder elsewhere. The entropy also goes up; it isn’t something that’s conserved.0598

Entropy is just constantly marching forward. In fact we can look at entropy; entropy is a one way arrow. We can think of it as the direction that times flows.0607

Entropy is always flowing in the direction of time moving forward. Things get more chaotic with time.0614

With that idea of things getting more chaotic with time, I’d just like to point out that the poets got it right. They might not have stated it scientifically, but poets have stated this intuitively for centuries.0622

For example, so dawn goes down to day, nothing gold can stay’. Nothing complex, nothing perfect can stay. Nothing beautiful is what’s its expressed in this poem, can stay for a long time.0632

That idea of break down is right there. Robert Frost. Another one, William Butler Yates, ‘things fall apart, the center can’t fold, mere anarchy is loosed upon the world.’0644

This is a part of larger poem, which actually has some different ideas going on, but that definitely applies to the notice of entropy, the fact that things just don’t last.0654

If this sounds interesting to you, there is a lot more poetry out there. I recommend it, go check it out. There’s some really cool stuff, more than just physics.0662

If you already like poetry, I think it’s really interesting to see how much there is a connection between the things that we study and the arts that are out there.0670

There’s a lot of connection between the science and the arts and it’s really interesting.0676

Back to the science. Engines in general, an engine takes in heat and it turns some of that into useful work and puts out the rest as exhaust.0680

An example of a car, it takes in gasoline, a complex molecule. It burns that to make the wheels spin through the use of the engine and some heat comes out of the engine and the engine compartment through the exhaust pipe.0689

Understand that that’s the general way of a car working? So we can come up with a really simple diagram, we can diagram this as a hot source that goes into some engine and then energy comes out of that engine in the form of work.0700

Then the rest of the energy goes into a cold sink. We’ve got some large amount of heat going into our engine and then out of that we’ve got work being turned out of that heat.0711

At the same time, some of it manages to get just lost to that cold sink. The best kind of engine would be something that gets lots of lots of work for very, very little energy.0721

The best kind of car would be where you put in a teaspoon of gasoline and then after driving your car you’ve got a liter of gasoline.0733

You put in a tiny amount of gasoline and it actually causes you to have more. But that doesn’t make sense because that would be a destruction of the conversation of energy.0740

We can’t get more work out than the energy we put in. At best, the best kind of engine from our point of view then, knowing that the conservation of energy is defiantly something we can’t beat.0748

The best engine would be one that’s able to convert all the heat energy we put into it into useful work. Every drop of heat energy gets turned into work.0759

That would be the best kind of thing. To describe this, to be able to measure the amount of heat that gets turned into work, we need to talk about efficiency.0767

How efficient something is. The amount of energy that has to go in for the amount of energy we get out.0774

We can compare the heat in to the work out. The efficiency is the work that we get out, w divided by the amount of heat we put in, the energy we put in.0780

The energy you get out divided by the energy you put in is the efficiency. The efficiency can be anywhere between 0 to 1 but no more.0789

We can also easily turn this into a percent by multiplying by 100. It would be great if there was an engine out there that did have a 100% efficiency that would be awesome.0796

It turns out that that’s not possible. A Carnot engine is a theoretical engine that can be proven to have the maximum possible efficiency.0806

It’s not possible to get better than a Carnot engine. Sadly a Carnot engine doesn’t even allow for 100% energy conversion.0814

The most that a Carnot engine will allows for is this: the upper limit on efficiency is connected to how hot your source is, how hot your heat source is, and how cold that exhaust is.0821

The best is going to be when there’s a really, really wide thing. The absolute best would be if your cold exhaust was absolute zero but that’s not possible.0832

You can’t have something in real life that is still at absolute zero. Once again you can’t perfectly insulate something.0839

If you were to have heat flowing into it, it wouldn’t be absolute zero for long. The upper limit is going to be 1 minus the ratio of the cold to the hot.0845

1 minus temperature of the cold divided by the temperature of the hot.0856

Notice temperature cold and temperature hot have to be measured in kelvin otherwise this formula won’t work because once again, if temperature cold was below zero Celsius, we’d have a negative number.0860

Suddenly we’d be able to have an efficiency that was greater one doesn’t make any sense.0869

We have to be talking in kelvin because we have to always be above that zero. We have to be working with kelvin.0873

But this is kind of disappointing. It would be great if there could be a perfect efficient engine but we can prove that it’s not because the best kind has got to be a Carnot engine and a Carnot engine has a maximum efficiency.0878

This efficiency isn’t what you’ll get in real life because the Carnot engine is forgetting the annoying things that come with real life, like friction and heat through other sources, the fact that you can’t have perfect insulation, those sorts of things.0889

It’s like talking about sort of a perfect theoretical thing and we can’t even create a perfect theatrical thing in real life.0903

So you’ll never see something in real life that is better than this. It’s always got to be less than that.0909

Ready for some examples. First example is a nice easy one to knock out of the park.0914

If a system has 100 joules of heat energy put into it and the system does 47 joules of work on its environment, how much will the internal energy have to be raised?0918

Well the first law of thermo dynamics is the heat in is equal to the change in the internal energy plus the work out.0926

Our heat energy was 100 joules, the work out was 47 joules. So we toss those numbers in and we get that 53 joules is the amount that the internal energy has gone up by.0939

Depending on the specific heat of what we’re dealing with we’ll get different amounts.0958

If we had a really low specific heat we’d get a higher temperature raise. If we had a really high specific heat we’d get a lower temperature raise.0962

We do know that the change in the internal energy is going to be 53 joules, whatever temperature that winds up connecting to.0967

Second example, what would be the efficiency of the system from the previous question?0974

Remember we had heat of 100 joules put in, we had a work of 47 joules and we had to change in internal energy of 53 joules.0978

First thing to notice, this is actually a red herring. We don’t care what the change in internal energy is. All we care is what’s the connection between the work out and the heat in.0985

Because that’s how we figure out efficiency. Efficiency is equal to the work divided by the heat in. Work out divided by heat in.0992

47 over 100, we get 0.47 is our efficiency; we would could also talk about as 47%.1002

We’ve got a 47% efficient engine, which is actually really, really, really good.1012

We’ll talk about why that’s so great. You’ll see precisely why that’s so great when we get to the fourth example but 47 is actually a really great efficiency to get.1016

Third example. We’re going to do this one without any math, but we will talk about it.1026

If you’ve got a bunch of coins scattered on the floor and you pick them all up and you stack them into one neat ordered column. You’ve created more order, right?1030

You’ve got this disordered bunch of coins sitting on the floor and you manage to bring it into one tightly bunched thing were they’re all together, they all have a unified temperature because they’re now touching.1038

Haven’t you made there less entropy? Haven’t you lowered the entropy in those coins? Yes, you have lowered the entropy in the coins, but you’ve introduced entropy to the rest of the world.1047

The rest of the universe will now have a total of more entropy. If we look at the entropy over the whole thing, we’re going to get more entropy.1058

Where is this coming from? How are we not violating the second law of thermo dynamics with the fact that we’re stacking these coins?1065

It’s because we can be sure in the fact that we’re introducing more entropy. How are we introducing more entropy?1070

Sure, the stack has less entropy, but there's other things out there. As you move around, one of the primary things, is you move around, you’re going to be generating heat.1075

Heat is generated by your motion. As you walk around the room picking up those coins, bending over. You’re going to introduce heat.1088

You’re going to cause heat to get put into it. The motion of the air molecules is going to become more frenetic, they’re going to be bouncing around, moving around more.1099

They’re going to become more random, more chaotic, less ordered, disordered. You’ve caused disorder in the air molecules by your raw motion, walking around the room and also by the heat generated off your body.1106

As you’ve done this, sugars in your body have been broken down. So you’ve got these complex chemicals that are supplying you with the energy.1116

So you’re breaking down these complex chemicals to be able to have less complex chemicals so you can have energy. You start with a complex chemical, you break it down into something simpler, some energy is released and that’s how your body is doing its thing.1125

It’s able to eat food and break it down into things that are simpler and so you get energy out of it. But in breaking it down you’re taking a complex thing and turning it into simpler.1136

In that case, you’re also once again releasing them. Just as you go around living, parts of your body, they start to degrade. You’ve got your skin cells breaking off, turning into dust.1145

Your skin cells are decaying along with varies other cells in your body. And your body is replenishing them, it’s causing more order, but this is going to all turn into waste products.1156

You’ve got these complex systems that are by nature just breaking down over time. Well you can go around doing something where you’re creating more order in the system.1163

On the whole when we look at the large picture more entropy is introduced just by the fact that you’re moving around doing anything.1172

The only way we could keep the entropy as low as possible would be to just let the coins sit and not have any effect on them and leave the door closed to it.1178

At least in that case no more entropy would be introduced. It would stay at its already disordered state but it wouldn’t become more disordered.1185

But as we go in and start to bustle around and do things we can cause some order to show up in one spot but on the whole more disorder will be introduced than order.1192

The entropy always goes up. Entropy wins. In the long run entropy is the winner.1200

Ready to do the final example. Iron melts a little bit after 1,500 degrees Celsius. As you start to go a little bit past that iron will start to break down and melt into a liquid.1211

If we’ve got a car engine made of iron, the absolute hottest we could run that engine would 1,500 degrees Celsius right?1221

We don’t…that would probably be…well okay first of all in real life, that would be magical because the oil that’s used to lubricate the engine to make sure it runs smoothly would be burned off, completely gone by that.1228

The gaskets involved, charred. The engine would just completely stop working way before 1,500 degrees Celsius. But we can defiantly see the…but it would be hard to figure out what the precise top level would be.1238

We can defiantly see one good place to say that the absolute top value is when you’re engine turns into a molten slag of iron, right?1249

When it turns just too liquid iron it’s no good anymore. We can say that the top operating heat would be 1,500 degrees Celsius, absolute top level for an engine.1257

That’s still higher than we could possibly get in real life but the absolute highest temperature we could operate an engine at is 1,500 degrees Celsius.1268

If that car engine is running on a 20 degree Celsius day, what’s the maximum efficiency we could get out of it?1275

Remember, the maximum efficiency is equal to…by the way, this guy right here he’s called epsilon, once again yet another of our friendly Greek letters, he’s epsilon.1280

Didn’t say that earlier but all of our efficiency has been using the letter epsilon. Our maximum efficiency is 1 minus the temperature of the cold sink divided by the temperature of the hot input.1293

If we managed to run our engine at its absolute highest temperature which is 1,500 degrees Celsius and sort of a ridiculously high temperature, higher than we could ever achieve in real life.1307

The absolute top we could pull off is 1,500 degrees Celsius and that’s going to be the absolute best we could have because the bigger the denominator, the better the efficiency we can get.1316

If we can get this number equal to zero we’ve got perfect efficiency. We want to make a giant denominator and tiny cold. Well what’s the cold sink going to be?1325

The cold sink, the best we could do would be the temperature around us in the atmosphere. We’re not able to drive around with a bucket of ice attached to us.1334

Although that’s an interesting idea, but in real life we’re going to have to deal with a bunch of other things.1343

We’ve got the fact that part of the sink is going to be engine compartment around us, we’ve got the engine compartment and that’s defiantly not going to be fully room temperature.1347

We’re going to at best be able to pull off that 20 degrees Celsius cold sink. Remember we can’t use Celsius though when we’re dealing with this because it’d be possible to drop Celsius into the negatives and then this whole formula would get screwed up.1357

We have to be working in kelvin since kelvin is the SI unit. If we want to make this into kelvin, we take each of these and we add 273.15. The cold is going to be 293.15 kelvin.1368

The hot in kelvin is going to be 1773.15 kelvin. The maximum efficiency, we plug both of those in and our maximum efficiency is 1 minus the cold, 293.15 kelvin divided by the hot, 1773.15 kelvin.1382

That comes out to 0.835 which is equal to 83.5%. Keep in mind 83.5% is ridiculously high because there is no way we could get a real life engine to operate at those kinds of temperatures.1406

If we’d tried to get a real life engine to operate at those kinds of temperatures, kapoot, there’s no way we’re going to actually be able to pull it off without completely destroying, just ruining our cars engine.1423

Real life we can’t get that kind of temperatures. That kind of temperature in the engine is just ridiculous. We’re not dealing with the best temperature we could have.1433

It’d clearly be better the way this works for us to be driving around in the winter, a colder temperature than 20 degrees Celsius, is something we could defiantly pull off.1442

But we’re not going to do way better, we can’t drop more than…if we were to manage to drop to -80 Celsius, that’d be colder than any day has ever been on Earth.1449

That’d be only dropping by 100, the efficiency just not going to bump up that much more.1457

83.5, when we’re dealing with this magical super engine is the best we can do.1461

To me at least, 83.5 that doesn’t sound that great. That’s getting pretty close to a B- if this were a test.1468

Think about this, efficiency is actually really, really hard to come by in real life. 83.5% is the best this magical engine can do. It’s able to withstand these crazy internal temperatures.1474

If that’s the best we can do for our engine that’s magical and remember this not even including things like the friction, the other real life forces that are going to occur.1486

This is this theoretical maximum for an already magical engine. If we were to introduce just a little bit of real life, those numbers are start to plummet.1494

In real life for an actual car engine, the theoretical amount that could put out. The theoretical for a real car engine operating at real temperatures, so theoretical car engine is able to pull off an efficiency of around 55% or so.1503

That’s pretty great but an actual car engine once you have to start factoring in all the friction resistances, all the pressure, the various turbulence that’s starts to happen, that sort of randomness that can’t be controlled for.1520

Actual car engines manage to pull of around 25% efficiency rate. Efficiency is really, really hard to come by. Most of the energy that we wind up breaking down from our chemical bonds, actually just goes to heat.1531

We aren’t able to get most of our heat to turn into work. Which is a real shame, because if we were able to manage to just double this, we’d be able to do great things with the amount of energy we have.1547

One of the best things we could do to get more energy is to be able to increase our efficiency, but there’s this hard limit to the best efficiency we can get.1556

That’s based on our hot temperature and our cold temperature. Unless we’re able to get those really far in difference, more importantly get a really nice cold sink temperature, you just can’t get that great in efficiency because of our Carnot maximum efficiency.1565

In real life efficiency is really hard to come by, so an actual car is able to pull off around 25%. Most of the gasoline you wind up burning in your car actually just goes to heating up the air around you, kind of disappointing.1581

But certainly really interesting. That’s the nature of thermo dynamics, a lot of stuff, all the order eventually falls into disorder. It’s not exactly the happiest of endings but that’s how things are going to go with time.1595

Entropy is the winner in the long run. We can at least have long period of order in thought and intelligence and great complex beings.1607

In the really, really long end, as the universe runs to its end, things will eventually tend to disorder and just have compete fall apart as the universe goes into just hot heat death mode as it breaks apart.1615

That’s a long, long, long time from now. For our purposes we can basically forget about that, we’re going to have the chance to live long complex interesting lives in a nice cool universe that hasn’t seen the long painful end of entropy yet.1628

Things are good for a long time to come so don’t worry about it.1643

Alright, hope that was interesting, hope you learned a lot and we’ll see you at educator.com later.1645

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