Electricity and electronics - the characteristics and applications of magnetic fields and electromagnetic induction
Students should have met the concepts of transformers, and magnetic induction in electricity generation at GCSE, but depending on their experience they may be limited to basic ideas.
The resources gathered here can be used to explain induction as well as give students a chance to build a basic motor or generator. There are resources from the IOP that are used to explain induction and electromagnetism to a level required for A level physics. These include questions and formula that may not be needed for this specification, but are good background for both the student and teacher.
There are also simulations from PhET that allow students to explore Faraday's laws on the computer. This is good for revision, but also to let all the students explore electromagnetism in an environment that can quickly be accessed, something not always possible in the lab with restrictions on amount of equipment.
Specification point:
- Electricity and electronics - the characteristics and applications of magnetic fields and electromagnetic induction
Electromagnetic Induction *suitable for home teaching*
This video shows how you can simply build a generator to demonstrate electromagnetic induction to your students as well as ideas for how to introduce the phenomenon.
The video can be used to show students directly, but is best used as a guide to inform how you might deliver the introduction to this topic.
Bozeman Science: Electromagnetic Induction
This video gives a good explanation of electromagnetic induction as a teaching aid or for students to use as a revision resource.
Paul Anderson who made the video uses his videos to "flip" the classroom and expects his students to use the videos before coming to class to experience a lab or further tuition. However you use the video it's a good format for students to use.
If you are going to ask students to work from the video you could add a set of questions that they can answer after viewing the video.
PhET Faraday Electromagnetic Lab
This set of simulations covers investigation of a magnet, electromagnet, induction, transformers and a generator. There are good notes and tips as well as sample lessons. You can download the simulator or run it from the browser.
The lab is good because it shows the the field lines. It can be used as a teaching aid on the interactive whiteboard or if students have access to computers it can be used directly to demonstrate the phenomena.
PHET Faraday's Law
This simulation allows students or the teacher demonstrate light a light bulb by waving a magnet. This could be used to help a physical practical demonstration or as a revision exercise. What is effective is that the simulation allows you to show the field lines of the magnet, as well as compare two different induction coils.
It is a subset of the Faraday Lab resource above and can be used by the teacher to air demonstration or by students as part of a computer based investigation.
Episode 412: Force on a Conductor in a Magnetic Field
A set of resources from the IOP that introduces Flemming's left hand rule and shows how the force on a conductor in a magnetic field can be calculated.
The series of experiments are best used as demonstrations in the lab to show how current carrying wires result in a magnetic force around the wire. They are a good introduction to electromagnetism and Fleming's Left Hand Rule.
While it is more challenging to set up, the trapeze is a good visual aid to see the how the direction of the current and field affect the force on the wire.
Episode 414: Electromagnetic Induction
A set of practicals and questions from the IOP that helps explain electromagnetic induction, including the concepts of flux, flux linkage and Lenz's Law.
There are a series of demonstrations that are good do show the effect of moving a conducting wire through a magnetic field. It is best to use an analogue ammeter or galvanometer as this shows the direction of the current more visibly where as a digital ammeter masks this. Alternatively a datalogger could be used.
The notes contain good diagrams which can be used in your lesson resources to show how the fields interact with the wire and there is a through explanation of flux and flux linkage and how this affects the size of the current.
Episode 415: Electric Motors
A set of resources from the IOP that describes the application of electromagnetism to the electric motor. Includes practical activities including building AC and DC electric motors.
It is worth getting students to build the electric motor described in this resource as it gives them an experience with the brushes and can lead to better understanding on how the motor operates. It is not too complicated a build, if the kits are prepared beforehand.
The demonstration with the electric drill is really useful to think about the opposing forces, energy transfers and efficiency of electromagnetic motors and inductors. Why are the coils getting hotter when the drill is loaded?
James Dyson Foundation: Make a Simple Motor.
A one sheet practical activity from the James Dyson foundation to build a simple motor from a screw, battery and magnet.
This is a good introduction to making a motor perhaps used before the previous resource as it only requires simple equipment to build. Students should be aware of the interaction between the current carrying wire and the magnetic field provided by the magnet.
Episode 416: Generators and Transformers
The main application of electromagnetic induction is that of generating electricity. This set of resources from the IOP provides discussion on electricity generation and mathematical treatment of transformers, including efficiency and the transformer equations.
The hand powered dynamo demonstration is a really useful one to show how the turbine powering the generator has to work harder when current flows, demonstrating conservation of energy.
The transformer experiments are really useful when teaching the transformer equations and showing that transformers are not 100% efficient.
Some of the questions in this resource are quite challenging, but can be used by the teacher to check student's mathematical understanding. All questions have worked solutions. The transformers questions 416-6 are particularly good for leading students through the concepts they need to develop.
Power Lines
A nice demonstration of power lines and why transformers are required to distribute electricity across large distances.
It's used at KS4 to demonstrate the use of transformers in electrical distribution, but if students haven't seen it, it is a good model to show how transmission losses occur and how transformers can reduce the losses.
Do perform a risk assesment for this activity, be aware that the voltages could get as high as 50V though the current will be low.
Electromagnetism
An older textbook by John Osborne on electromagnetism that covers the physics as well as the historical developments in electromagnetism and gives many examples of applications.
This book is a great resource for clear diagrams and pictures as well as showing applications of electrical induction in electrical musical instruments like guitars and amplifiers.
