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Vincent Selhorst-Jones

Vincent Selhorst-Jones

Magnetism

Slide Duration:

Table of Contents

I. 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
What's Different About Multiple Dimensions?
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
What About Acceleration?
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
II. 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
Newton's 2nd Law: Advanced Examples

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
A Quadruple Pulley Lifting System
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
Friction is Not About Weight
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
III. 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
IV. 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
V. 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
VI. 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
Long Radio Waves & Radio Waves
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
VII. 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
Wait! What About Pressure?
22:30
Wait! What About Pressure?
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
Radiation
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
The Mole and Avogadro's Number
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
VIII. 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
Faraday Cage
8:47
Introduction to Faraday Cage
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
IX. 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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Lecture Comments (2)

1 answer

Last reply by: Professor Selhorst-Jones
Tue Oct 21, 2014 9:50 AM

Post by Jamal Tischler on October 21, 2014

Great course ! Can you record more physics lectures ? Something harder with more problems ?

Magnetism

  • Every magnet comes with two poles. Just like electricity, like poles repel each other, while opposite poles attract.
  • Like electricity, we can describe the space around a magnet with a magnetic field and visualize it through the use of magnetic field lines.
  • Unlike electricity, it is not possible to separate these poles from each other. Magnets always come as a dipole: two poles together.
  • Moving charge creates a magnetic field.
  • On an atomic level, all atoms involve moving charge (the electrons). Thus, they have many small magnetic fields. Normally, the random distribution of these fields results in no net effect.
  • However, in some materials (such as iron), it is possible for these magnetic fields to all align and create a temporary or permanent magnet.
  • Since moving charge creates a magnetic field, we can run current through a wire to create a magnetic field in the space around it.
  • Through some clever arrangement, we can run current through some loops of wire, create a magnetic field, and then have it interact with another magnetic field, causing those loops to spin. Spin them with enough force, and you've got an electric motor.
  • The reverse also works: a changing magnetic field induces a current in a conductor. If you place a loop in a magnetic field and make it spin with enough force, you've got an electric generator.

Magnetism

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
  • Magnet 1:27
    • Magnet Has Two Poles
    • Magnetic Field
  • Always a Dipole, Never a Monopole 2:22
    • Always a Dipole, Never a Monopole
  • Magnetic Fields and Moving Charge 4:01
    • Magnetic Fields and Moving Charge
  • Magnets on an Atomic Level 4:45
    • Magnets on an Atomic Level
    • Evenly Distributed Motions
    • Unevenly Distributed Motions
  • Current and Magnetic Fields 9:42
    • Current Flow and Magnetic Field
    • Electromagnet
  • Electric Motor 13:11
    • Electric Motor
  • Generator 15:38
    • A Changing Magnetic Field Induces a Current
  • 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

Transcription: Magnetism

Hi welcome back to educator.com. Today we’re going to talk about magnetism.0000

Here’s some things to think about, an electric plant running on coal, a speaker pumping out music, a compass pointing to the north, an electric car driving down the road, and a magnet holding up a report card on a refrigerator.0006

What do all these things have in common? Now you were probably able to guess because of the title to this lesson, magnetism.0018

They’re all based on the existence of magnetism. None of these things would be able to run if it weren’t for magnets.0026

When we work through magnets, when we’re working through this lesson, we don’t have the math yet to be able to quantitatively describe what’s going on.0033

We need calculus to really understand this and also have a slightly better grasp on some things that go on in vectors and so we’re not going to introduce those math concepts for the small dip that we’re going to have in magnetism.0041

We can still understand a lot of things that are going on qualitatively, like we did with entropy in thermodynamics, we didn’t define anything mathematically but we were still able to get a really good feel for the idea’s going on.0052

That’s what we’re going to get here with magnetism which is great because it’s going to give us a bunch of things to think about and it’s going to help us understand how our modern existence is.0063

I mean, is completely shaped by the fact that magnetism is a force. If it weren’t for that we wouldn’t have electricity running through our walls pretty much.0071

Its incredibly important. Magnetism, really interesting stuff. We don’t have the math to talk about it but that’s okay, we’ll still be able to forge on.0079

Every magnet has two poles, a north pole and a south pole. Just like in electricity, like poles repeal each other while opposite poles attracts.0088

If you put two north poles next to each other they push away. If you put to south poles next to each other they push away.0098

A north pole and a south pole will attract one another. They’ll have a force pulling each other together.0102

Just like in electricity we can also describe the area around a magnet as a magnetic field. We can draw on these magnetic field lines.0108

In this case, the magnetic field lines, they go from the south to the north because once again we do things from the North’s point of view.0115

Then the north is going to push it away, suck it back to the south and as we slid through, we’re going to get these circles moving like this.0122

The north pushes it away but then the South Pole pulls it in and it comes back and then shoots through the magnet.0130

We can draw on magnetic field lines on any of these things. This idea of a magnetic field is really important.0136

Another really important thing though is unlike electricity it’s impossible to separate these two poles from each other. With electricity we could put a bunch of charge on one object and carry that object off somewhere else.0143

We’d be able to separate the positive charges from the negative charges as much as we wanted. Magnetism you can’t separate the poles of a magnet. Magnets always come as a dipole, two poles. They always come stuck together.0154

Even if we took a magnet and broke it into two pieces it’s not like we get the north half and the south half. Now we just have the north half also has it’s south half.0168

The south half now also has its north piece. The other part is always there, it’s just a gradation of south to north, and so if you take it, it’s just the difference between north and south.0176

There’s always going wind up being this magnet coming up. We’re always going to wind up having a dipole no matter what we do.0185

That said, we have never found a monopole and just because we haven’t found a monopole, one pole by itself, doesn’t mean it’s absolutely impossible. It might be possible to get things out from a dipole.0192

I have repeatedly said that its impossible and all these sorts of things but that doesn’t mean that there’s no way that it could be….just because I’ve said its impossible doesn’t mean it’s actually impossible.0204

I’m just saying so far we’ve never found it. It’s really unlikely that we’re going to find one, we haven’t found it, but it doesn’t completely bar the possibility.0216

Like all things in science, we have to be prepared for unexpected changes. Things that we are not ready to…our theory isn’t ready for yet.0225

That said, our theory is pretty strong at this point, it seems pretty likely that we’re not going to find a monopole.0234

Here’s the really amazing thing about magnets. This is mind-blowing. A moving charge creates a magnetic field and the space around it. If you take a charge and slide it through the air, you slide it through space; the area around it has a magnetic field as long as it’s moving.0242

As long as it’s changing location a magnetic field is around it. We won’t get into the why, it involves things that are a little beyond us at the moment.0262

It involves moving electric fields and connections to special relatively and things that we haven’t talked about and are not going to get the chance to discuss.0271

This is amazing. This is huge ramifications which we experience daily. Let’s look at why these charges, why moving charge would cause magnets in like a bar magnet, that we can stick to a refrigerator.0280

Even when an atom is still the electrons are moving. They orbit the nucleus, so they’re moving around the nucleus and at the same time they’re spinning like tops.0297

We’ve got some nucleus, some super dense nucleus in the middle and around we’ve got an electron moving. The electrons moving around it in a circle and as it’s moving it’s also spinning itself.0305

Its spinning like a top as its orbiting the nucleus. That combination of its own motion and its spin and actually its more of the spin than its own motion creates a magnetic field.0319

Its moving charge, so even atom and every object is full of moving charge. Since every object has many, many, many atoms inside of it, each one of those atoms has a lot of moving charge and all those moving charges create magnetic fields.0331

In most objects these electric charge motions are evenly distributed on the whole, half the electrons create a magnetic field pointing one way while the other half point the other direction.0346

The spins wind up…one of them is spinning clockwise, the other is spinning counter clockwise effectively.0356

Because of that, that one of them points one with its magnetic field, the other one points the other way and so they cancel out to nothing.0362

We experience the magnetic field as being nothing. Just like with net charge, there is a lot of positive charge, there’s a lot of negative charge, they’re all right next to one another.0368

From our point of view there’s no charge, there’s no net charge. Just like there’s no net magnetic field.0376

However, in some materials like iron, the motions are unevenly distributed. There’s more of one electron spin type than the other. If we’ve got more of one electron spin type than any other then we’ve got a little bit more of magnetic field than the other type of magnetic field.0382

There are these many tiny magnetic domains each operating as its own magnet. This is a very blown up piece of magnet where this…this is actually not a magnet, this is just some chuck of iron.0399

Each piece of this iron has its own little magnetic domain. Each one of these magnetic domains winds up having its own magnetic field direction.0411

If it’s like this and it just a bunch of magnetic fields, they all cancel each other out. On the whole these tiny magnetized sections, there’s so many of them, they’re all pointing randomly. We don’t notice anything, the iron has a lot of stuff happening inside of it but since it’s pointing all directions at once it’s just noise.0424

It just cancels itself out, nothing really comes of it. If we bring up a magnet near the object, all of a sudden each of those sections, each of those magnetized domains…each of those magnetic domains, they’re each going to spin into alignment and we’ve created a temporary magnet.0442

We’re going to get all those electrons lining up; they’re all going to point the same direction because there’s this other magnet near them.0460

We’re going to temporarily magnetize this chunk of iron. We’ve got this permanent magnet that shows up on the scene.0466

Each one of those magnetic domains goes “Oh, those guys are pointing that way. I’m being pushed…I’m now in line with that”.0474

It’s in line with that, that happens to all of its friends, so all of the friends are in line and they’re also now reinforcing their own magnetism.0481

Each one of the guys, if this guy tried to spin on his own, if he tried to spin back to some other direction even without the magnet there.0487

If all the other guys were already pointing in one way, they all say “Nope, you got to go this way”, and they’d all push him back into position.0496

As long as the whole group is moving as one, the whole group is pointed in some direction; any person who randomly starts to drift off will wind up getting pointed back to it.0502

If we go and we remove the magnet, most pieces of iron, they are not so magnetized over the course of being next to that other magnet that they’re just going to wind up their own random thermo motion.0512

The atoms moving around, it’s going to wind up canceling out and they’re going to sort of bounce their own magnet domains until they’re eventually each random again and we’ll have lost the magnetic-ness.0524

This is why when we take a bar magnet, some sort of magnet, and we stick it to a fridge, the fridge has iron inside of it. We stick it to the fridge and the fridge magnetizes to it. It puts a force on it because on the other side, that iron goes “Oh, it’s a magnet.”0532

It all flips in magnetic direction, so now we’ve got south, north, they stick together, they’ve got a force. We pull the magnet away and we stick up another piece of iron in its place, it doesn’t do anything because already demagnetized itself.0548

It’s lost that magnetism in the period of time it took to just put up a nail or something next to the spot that had had magnet.0561

We’re able to magnetize normal pieces of iron by putting them next to a magnet because on an atomic level they have this magnetic domains where they’re ready to take a magnetism, they just need to have one put over the whole group.0569

Back to that idea of moving charge creating magnetic field. If a moving charge creates a magnetic field around it then it would defiantly follows that current flowing, flowing current will create a continuous magnetic field.0584

If we have an amp of current flowing down a line we’re going to have a magnetic field around that amp of current.0598

The magnetic field makes a circle around the wire. If we’ve got a wire going like this, it’s going to circle around it so it’s going to wind up doing something like that.0605

At the higher up, it’s going to circle…it should be about the same size but it’s going to wind up circling around it.0619

If my arm was the wire, it’s going to go like this around it. At each point we’re going to see this magnetic field curving around it. The idea is the right hand rule, if you put your thumb in the orientation that current is moving and then curl your fingers on your right hand.0626

Thumb with the current and then curl your fingers that’s the direction that the magnetic field is going.0641

If we did the same idea and instead of just having a line we’d had loop like this. Well if we look inside of that loop, we’re going to wind up having a…never said to be the best artist.0647

We’re going to wind up having a bunch of different magnetic things. Along that current, if the current is flowing like this as it goes through, we’re going to wind up seeing…actually I might have put those blue on the wrong way, but we get the idea.0666

You could imagine it yourself, you could curl out a single loop in the air using your right hand and you’ll be able to see it. Kind of hard to draw this stuff, sorry I’m just not the best drawer.0686

We can create a loop that’s got a magnetic field going around it. What if we make a bunch of loops? The more loops we have for a given current, the more times that current is going to have the change to create a magnetic field in the same location.0697

If we stack our loops so it comes in and loop, loop, loop, loop, loop, loop, loop, loop, and then goes back out, well that means that all of a sudden we’ve got this massive magnetic field going through.0711

We’ve got this huge magnetic field because we’ve stacked all of those loops and we’re talking, in reality when you stack this in real life and real engineering, we’re talking hundreds maybe even thousands or even more loops.0724

Lots of turns in wire. We can repeated put down many, many loops and by having the current flow through all those loops at the same time, we’ve got a bunch of charged moving in one combined area.0735

We’ve got a really strong magnetic field. Each loop backs up the magnetic field. Since each loop provides one magnetic field worth of strength depending on the strength of the current running through.0747

If we have a thousand loops, we’re going to multiply that by a thousand because we’re layering it one on top of the other. We’ve got a thousand times what it would have been if it was just one.0757

If we’ve got many loops of wire and we run current through it, we’ve created an electromagnet. We’ve created a magnet that operates when electricity runs through it.0767

When we run current through all these loops we create a magnet. It becomes a magnet because we’ve run current through it, because we’re able to put many magnetic fields on top of it, we can make it into a very noticeable, very, very strong magnet.0776

This idea is what gives us the ability to have electric motors. If we run a current through a loop or loops of wire it’s going to create a magnetic field.0792

If we have that loop and in general, in real life we’d wind up having to engineer with a loops, many, many loops of wire but for ease we’ll say it’s just one loop to imagine it.0803

If we have a loop and we run current through it we’ve got a magnetic field. Then if we place this loop or these loops into another magnetic field, those magnetic fields will interact.0813

The magnetic field of our loops compared to the magnetic field of the permanent magnet it’s next to, we’re going to have two magnetic fields. Those two magnetic fields will interact and a force is going to be applied to our loops.0823

Now with some clever engineering we could put that loop on an axel and we could have the current constantly flow through it, this is the clever part of engineering and we’ll be able to get the force to not just push on it once, but we’ll be able to get it to push on it and push on it and start spinning it.0835

We’ve got some loop of wire and then we manage to have that magnet push down this way so it spins it, it torque it.0852

If we’ve got this attached to some axel like this, where the wire is running down on either side of it.0863

Then we’re able to run a current through it, the axel starts to spin so we’ve got this spinning axel, we’ve got current running through it creating this…we’ve got current running through it creating a magnetic field.0873

It’s interacting with the other magnetic fields where it’s providing a force. That force provides a torque because its pushing on one edge, that we design it to make sure it pushes on one edge and so that torque causes the whole thing to start to spin.0884

We get it to spin fast enough by putting enough current through it by letting it run for a while; we’ve got a spinning axel. A spinning axel is the output shaft of a motor.0897

If we get something to spin then we can put that spin into something else and that’s exactly what happens in the electric motor of a car, the electric motor of an RC, the electric motor of…any electric motor is something has managed to spin.0907

We get something to spin up. This is what happens in a fan, in fan blades. The electric motor there is causing something to spin and it’s causing the spinning because it’s got this resistance between magnetism and the magnetism of the loop.0917

We can create a motor by just having electricity. This is really cool. Now if we do the reverse of it, it turns out that the reverse actually works.0935

Moving charge creates a magnetic field. It turns out the reverse is also true. If a change in magnetic field will induce a current. If we have a magnetic field change around a loop, change around a conductor, it’s going to induce current.0943

Its going to put a voltage on it. If we pass a loop of wire through a magnetic field, say we’ve got some magnetic field just hanging out here and then we take a loop of wire and we push it this way through it.0958

As it passes through the magnetic field it’s going to wind up having some current because it’s going to see a change in magnetic field.0975

It’s moving through it so it’s going to see a change. Alternatively we could put it in place and just spin it. As it spins, it’s going to see different ways of looking at that magnetic field, so from the point of view of the spinning loop, it’s constantly seeing new kinds of magnetic fields.0983

It’s seeing a constantly changing magnetic field. If we spin the loop in a stationary magnetic field, that loop will produce current. If we mount that loop on an axel and then we spin that axel and it’s in a magnetic field, that loop is going to generate current.1000

If we have a bunch of loops on that axel and then we spin the axel really quickly through a motor, then we can generate large quantities of current and this is the idea that powers all of the electric factories, pretty much almost everyone, not true for solar cells, but most electric factories are going to have something like this.1018

If we have an electric power plant it’s going to be based on this idea; coal uses that coal to boil water to cause a steam turbine to spin. That turbine is the spinning thing for this loop. It’s in a magnetic field so it spins, we create electricity.1043

In a nuclear power plant it’s the same idea, we’ve got rods of nuclear…we’ve got nuclear elements that are putting out energy, the put out heat energy as they decompose, as they break down.1062

We’re going to wind up using that heat energy to boil water. We boil water; once again we push it through a steam turbine. That steam turbine spins this loop of wire, we get electricity.1078

A hydroelectric dam, a hydroelectric plant does it even more directly. It just has a flowing amount of water, either going a waterfall or in a river and it just immerses a turbine, the flowing water spins that turbine, that turbine spins the axel, spins the loop.1090

Once that loop is spinning in the magnetic field, boom, we’ve got electricity. This is a really, really cool idea. It’s the reason that this connection between magnetism and electricity, it’s the reason why we can all have TVs, why we can have power outlets that we can plug all of this energy into.1107

Is because we can change these sources of energy, we can move our energy around. It’s not that the electricity is creating energy; it’s that we’re taking the kinetic energy of the water.1123

We’re taking the chemical energy of the coal and putting that into kinetic energy of steam and then taking that kinetic energy and we’re converting it into electricity which we then pipe to our house.1134

Any of these things. We’re converting some form of an energy into something that manages to get it put into electricity and that change over moment, when it changes over from whatever it was before, whatever kinetic….it becomes kinetic energy to spin the turbine and through magnetism is manages to transform to electricity.1142

This is really, really cool and this is the reason we have technology. This is the reason I’m currently able to teach you through the internet is because the fact that we’ve these generators working.1159

That there’s this really cool thing about magnetism. This is just awesome. Alright, we’re ready for some examples.1169

If you isolate a magnet from air currents and you support it in some way that it can rotate frictionless, you’ve created a compass.1176

That compass, its North Pole will eventually point to the Earth’s geographic North Pole. Now it’s actually not precisely the Earth’s geographic North Pole but it’s pretty close for the purposes of exploring the wilderness, it does a great job.1183

It points really close to the North Pole so we can treat it as pointing to the North Pole. If it’s the North Pole of the compass, the magnetic North Pole of the compass pointing to the Earth’s North Pole, what kind of magnetic pole is the Earth’s pole?1196

Remember, North to North repulse. North to South attracts. If we know, if we know that the compass is defiantly a North Pole which we’ve been told that, that’s how it works, that’s how it’s defined.1211

If the compass has a North Pole and it’s spins to point to the Earth’s geographic North Pole, then the magnetic pole has to be South because that’s the only one that would attract it.1231

The Earth North geographic is actually a south magnetic, pretty cool. Second example.1242

To run a generator or an electric motor you need some sort of powerful magnetic field. How could you create such a field if you don’t have a supply of extremely powerful permanent magnets?1258

Even if you did have a supply of extremely powerful permanent magnets, they actually…real life generators pretty much don’t run on permanent magnets in them.1268

What they run on is the idea that you talked about earlier; electromagnets. If you’re going to have…if you need to be able to have some power, some control over what you’re going to have be the field that you want it to run through.1276

If you want to have precise control over what kind of current gets put out, you’re going to need some control over that field or you might want some control over that field.1290

We need to be able to choose it ourselves and to choose it ourselves we use an electromagnet. Then we can choose how many loops of wire we use and what kind of current we run through it.1299

Of course you’ll need some way to generate the current through…for this yourself, so you might need either some sort of strong battery to get it started and then you can just leech off of the electricity being generated in the first place.1307

Off of the generator or you could just crank it by hand or have some other generator that setting it up. All sorts of different possibilities but you are going to have to use some sort of electromagnet.1320

Or you could use extremely powerful permanent magnet but if you don’t have access to them, this is the trick; you’re able to use an electromagnet to generate the magnetic field so that you can then generate even more electricity.1332

You’re not getting something for free here by the way. I just want to point out that really quickly. It’s not that you get free electricity because it’s being….it doesn’t spin freely.1343

The magnetic forces are now actually….the loop has…since it now has current flowing through it, not it has an induced magnetic field as well.1351

That magnetic field is actually fighting it out with the other one so it’s trying to reduce its spin. We don’t get…there’s no free lunch in physics.1359

You don’t manage to spin it and then just get this free unlimited supply of electricity, free unlimited supply of energy.1366

Conservation of energy wouldn’t be happy with that. It’s spins and then its own magnetic field resists the magnetic field that’s already there and so it tries to slow itself down.1371

That’s what the work we have to put into it and the work that we put in to overcome it is the energy that we get out of it electrically.1381

Final example. One way to damage or destroy the magnetic properties of a permanent magnet is to heat it or repeatedly strike it.1388

Why? Remember what a magnetic looks like. If you have an iron magnet, you’ve got all the little arrows pointing in the same way. When it was just a normal piece of iron they were all pointing in random directions.1397

When you get a real full on magnet out of iron the same thing happens, it just manages to point the same way and then stay that way.1410

You’ve magnetized it enough that it’s able to stay locked in and if one guys tries to rotate, he’s going to wind up being pushed back into the orientation that he was by all his neighbors who were also currently in their location.1418

What would happen if you heated it? Remember heat means kinetic energy, if you heat it then you cause the whole thing to shake. This guy shakes, this guy shakes, this guy shakes, this guy shakes, they all start to shake.1430

If they all start to vibrate then it means that they’re vibrating, they’re off a little bit. If they’re off a little bit they might start to point in the wrong direction.1444

If they all start to point in the wrong direction simultaneously they no longer have that peer group effect where they’re all holding each other pointing in the right way.1450

They start to all vibrate a little bit, they start to all get off their track and boom it’s lost. We lose the magnetic property.1459

They’re going to start to disappear and then they’ll start once again pointing in random directions. Now if only one or two manage to turn to a random direction it might manages to remagnetize itself because it could be pushed back into alignment by its peers.1466

If they all start to turn because we’ve heated it up enough, if we heat it to red hot they’re all going to defiantly start to change and jostle and they’re going to lose its magnetic properties.1479

Same basic idea behind striking it. If we strike it, we literally jar, we literally shake those atoms. We might shake those atoms so much; shake those connected molecules that they’re going to wind up starting to spin.1490

They spin a bit and once again we manage to set off this domino effect where they all sort of spin the wrong way and we lose the magnetism. We’ve demagnetized the magnet.1503

Alright, I hope that gives you some idea of magnets and what’s really going on there and why it’s so incredibly useful and important for all of humanity that we have…that there is this thing in nature.1511

I suppose that’s true of all the natural forces. The electric force, the gravitational force, you and I wouldn’t be here if the gravitation force weren’t holding us to the Earth and keeping us spin around that nice warm Sun.1523

We’ve got a lot of cool things happening in physics and all of it coming together is the reason we have the things we have. Hope you’ve learned something; hope you’ve had a great time.1533

It’s been a real pleasure teaching this class and best of luck.1540

See you later on educator.com. Bye.1544

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