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      • 5.4 Electromagnetic Induction >
        • 5.4.1 Magnetic Flux
        • 5.4.2 Faraday's Law
        • 5.4.3 Lenz' Law
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Electromagnetic Induction

PREVIOUS LESSON                                                                                                                               NEXT LESSON
In the previous set of lessons, we concentrated on the behaviour of moving charges in magnetic fields.
However there is a flip-side.
If an electrical charge experience is a changing magnetic field, or more correctly flux, it will begin to 'move'. This concept is called electromagnetic induction.
In the series of lessons we will discuss the key terms you need to understand, Faraday's law and Lenz law,  which underpin our understanding of induction, and include some applications of induction, including transformers and electromagnetic braking.
 

1. Flux and EMF Explained

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worked solution
going deeper
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video
An important concept in electromagnetic induction is the idea of flux. Flux has numerous meanings within physics. In this concept in this context we will be examining it in terms of magnetic field lines.
This video also discusses how electromotive force, or EMF for short, is related to the idea of flux change.

 A summary of flux , useful for review
worked solution
coming soon
going deeper
resources
 

2. Faraday's Law demonstrated and explained

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worked solution
interactive
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If a wire experiences a changing flux it also experiences an EMF, as discussed in the previous video. More correctly EMF that is generated is directly proportional to the rate of change of flux this is called Faraday's law.
This video demonstrates this in action and explains the principles behind Faraday's Law.

Check out the interactive which allows you to consolidate your understanding of Faraday's Law
This video provides a a quick summary - useful for review
worked solution
Picture
interactive
Explore faraday's Law with this pHET animation
resources
 

​3. Eddy Currents and Lenz Law

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interactive
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If a conductor experiences a changing flux, and thus experiences and EMF, if the charges are free to flow, currents are induced. In solid materials such as pipes and sheets of metal, these currents become eddy currents. However these eddy currents will therefore also generate their own magnetic fields thereby interacting with the magnetic field that generated them. This leads to an important principle called lenz' Law.
​See the following two videos that demonstrate lenses law in action and also provides an application called electromagnetic breaking.

Down a Pipe
Drop a magnet down a pipe and it does not fall as you expect. Physics involved
Electromagnetic Braking
Similar to the lesson above, but now looking at electromagnetic braking
There are a number of great demonstrations that work on the principle of Lenz's Law. Here I examine a few of them
A quick summary of Lenz's Law, useful for review
interactive
 

4. Motors and Generators compared

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Induction and AC motors
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Since a current bearing wire has a magnetic field, placing the same wire in an external magnetic field will mean it will experience a force. This is known as the motor effect.
​See Resources for using a current balance which examine the motor effect
Induction and AC motors
In this video I discuss AC motors, in particular, synchronous motors. I then lead on to the physics behind induction motors
interactive
 

5. Understanding Back EMF

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worked solution
going deeper
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In the previous set of lessons we discussed the principles in an electric motor, that is a coil of current bearing wire will experience a force in a magnetic field. If in a loop this results in a torque and the motor turns. However the loop of wire is now experiencing a changing flux which should result in induction. This leads to important consideration called back EMF
The motor effect and induction at the same time!

​
This video provides a a quick summary - useful for review
worked solution
going deeper
coming soon
 
 

6. Transformers Explained

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worked solution
The Induction Coil
problems
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Most of us have heard of transformers. More than likely the device you are reading this on is plugged into either a 240 V or 120 V power supply, but only requires a much lower voltage. Do you have a transformer that transforms the higher voltage into the lower voltage. But how does it work? In essence it's a simple application of conservation of energy and Faraday's law. This video not only discusses the key principles but also the mathematical models associated with transformers.
Check out the sample solution, and try some problems yourself.
Also watch the video on the induction coil, which is used in many classrooms and is simply a transformer.
worked solution
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The Induction Coil

​Another application of induction, a type of step up transformer
problems
transformer worksheet
This video provides a a quick summary - useful for review
 
 

7. How well do you know induction?

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induction Quiz

​Test your understanding of induction. So do the quiz and try to get full marks

Then check your understanding if necessary with the video
more questions

9. How well do you know the transformers?

quiz
more questions
quiz
Transformers Quiz

​Test your understanding of transformers. So do the quiz and try to get full marks

Then check your understanding if necessary with the video
more questions

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  • Home
  • Lessons
    • 1 Foundations >
      • 1.1 Dimensions and units
      • 1.2 Mathematic skills
      • 1.3 Graphing
      • 1.4 Vectors
    • 2 Mechanics >
      • 2.1 Kinematics 1D >
        • 2.1.1 Kinematics Intro
        • 2.1.2 Acceleration
        • 2.1.3 Graphing Motion
        • 2.1.4 Equations of Motion
      • 2.2 Kinematics 2D >
        • 2.2.1 Relative Motion
        • 2.2.2 Projectile Motion
      • 2.3 Forces >
        • 2.3.1 Newton's Laws
        • 2.3.2 forces in equilibrium
        • 2.3.3 Normal
        • 2.3.4 Friction
        • 2.3.5 Forces and Pulleys
      • 2.4 Momentum and Energy >
        • 2.4.1 Momentum
        • 2.4.2 Energy
      • 2.5 Rotational Mechanics >
        • 2.5.1 Circular Motion
        • 2.5.2 Angular Velocity
        • 2.5.3 Circular applications
        • 2.5.4 Torque
      • 2.6 Gravity >
        • 2.6.1 Gravitation
        • 2.6.2 Orbital Motion
        • 2.6.3 Kepler's Laws
        • 2.6.4 Gravitation and Energy
    • 3 Waves and Optics >
      • 3.1 Wave Phenomena >
        • 3.1.1 Wave Types
        • 3.1.2 Superposition
        • 3.1.3 Interference
        • 3.1.4 Inverse Square Law
        • 3.1.5 Modulation
      • 3.2 Sound >
        • 3.2.1 Beats
        • 3.2.2 Doppler
        • 3.2.3 Resonance
        • 3.2.4 Standing Waves
      • 3.3 Physical Optics >
        • 3.3.1 Light - a history
        • 3.3.2 Double Slit Diffraction
        • 3.3.3 Light - its speed
        • 3.3.4 Light as EMR
        • 3.3.5 Polarisation
        • 3.3.6 Spectroscopy
        • 3.3.7 Scattering
      • 3.4 Geometric Optics >
        • 3.4.1 Reflection
        • 3.4.2 Refraction
        • 3.4.3 Lenses and Images
        • 3.4.4 Dispersion
    • 4 Thermodynamics >
      • 4.1 Heat and Temperature
      • 4.2 Specific Heat Capacity
      • 4.3 Latent Heat
      • 4.4 Blackbody Radiation
    • 5 Electricity and Magnetism >
      • 5.1 Electrostatics >
        • 5.1.1 Charge
        • 5.1.2 Coulomb's Law
        • 5.1.3 Electric Field
        • 5.1.4 Voltage
      • 5.2 Circuits >
        • 5.2.1 Ohm's Law
        • 5.2.2 Series and Parallel Circuits
        • 5.2.3 Electrical Power
      • 5.3 Electromagnetism >
        • 5.3.1 Moving Charges in Electric Fields
        • 5.3.2 Ampere's Law
        • 5.3.3 Charge in Magnetic Fields
        • 5.3.4 Motor Effect
        • 5.3.5 DC Motor
      • 5.4 Electromagnetic Induction >
        • 5.4.1 Magnetic Flux
        • 5.4.2 Faraday's Law
        • 5.4.3 Lenz' Law
        • 5.4.4 Back EMF
        • 5.4.5 Generators
        • 5.4.6 Transformers
        • 5.4.7 Induction Motors
    • 6 Modern Physics >
      • 6.1 Relativity >
        • 6.1.1 Michelson Morley Experiment
        • 6.1.2 Special Relativity
        • 6.1.3 Special Relativity Evidence
      • 6.2 Atomic Physics >
        • 6.2.1 JJ Thomson and the electron
        • 6.2.2 Millikan
        • 6.2.3 Rutherford
        • 6.2.4 Chadwick
      • 6.3 Radioactivity >
        • 6.3.1 What is Radioactivity
        • 6.3.2 Half Life
        • 6.3.3 Binding Energy
        • 6.3.4 Strong Nuclear Force
        • 6.3.5 Fission
        • 6.3.6 Fusion
      • 6.4 Quantum Physics >
        • 6.4.1 Planck and the Blackbody
        • 6.4.2 Photoelectric Effect
        • 6.4.3 Bohr Model
        • 6.4.4 de Broglie and Matter Waves
        • 6.4.5 Compton Effect
        • 6.4.6 Schrödinger Equation
        • 6.4.7 Heisenberg
        • 6.4.8 Lasers
      • 6.4 Particle Physics
      • 6.5 Solid State Physics
    • 7 Astrophysics >
      • 7.1 Olber's Paradox
      • 7.2 Stellar Spectroscopy
      • 7.3 Determining Stellar Distances
      • 7.4 Star Magnitude
      • 7.5 Star Temperature
      • 7..6 HR Diagram
    • 8 Medical Physics >
      • 8.1 Ultrasound
      • 8.2 X-ray
      • 8.3 PET scans
      • 8.4 MRI
  • curriculum specific
    • NSW >
      • NSW curriculum >
        • Year 11
        • Year 12
      • HSC question per Module
      • HSC Exam review >
        • Downloads/notes
    • QLD curriculum
    • IB curriculum
    • SAT curriculum
    • AP Physics 1&2 curriculum
  • Resources
    • Review videos
    • Shorts
    • Formula Sheet
    • tools >
      • Calculator
      • Oscilloscope
    • data sheet
    • for students >
      • recommended physics sites
      • Review and Tips
    • for teachers
    • Blogs >
      • Podcasts
      • PhysicsHigh blog
    • About >
      • Who am I
      • FAQ
      • Fun
      • Contact