Eddy Current Educational Circuit Board
Code B07MZD119M
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- Sold by Gurukul Technicals Institute, Delhi.
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In this project guide
Physics
About this model
This educational circuit board demonstrates eddy currents, the swirling currents induced in a piece of metal when the magnetic field through it changes. It suits students who want to show a striking effect of electromagnetic induction and explain its real-world uses.
How it works
The science behind it
The idea the model demonstrates, in words you can use in your report and when you explain it.
When the magnetic flux through a piece of metal changes, an emf is induced in it by Faraday's law, and because the metal is a conductor, currents flow in closed loops inside it. These loops look like whirlpools, or eddies, in water, so they are called eddy currents. By Lenz's law they always flow in a direction that opposes the change producing them. This has two results. First, they create a force that opposes motion: a strong magnet dropped through a copper or aluminium pipe falls slowly, and a metal plate swinging between the poles of a magnet stops quickly. Second, they heat the metal, which wastes energy in transformer cores; this is why cores are made of thin insulated laminations that break up the current paths. Useful applications include electromagnetic brakes on some trains, induction furnaces, and the induction cooktops in many Indian kitchens, where eddy currents heat the base of the vessel directly.
Make it yourself
Make an eddy current brake model yourself
Build your own version from scratch, or use the steps to understand how the ready-made model is put together before you present it.
What you need 10
Step by step 9 steps
An adult cuts two identical aluminium plates, about 8 cm × 6 cm, and cuts several deep slots in one so it looks like a comb. File all edges smooth.
Fix each plate, and the plastic plate, to the end of its own arm, with a hole at the top of each arm for the pivot, so all three pendulums are the same length.
Fix two magnets on each bracket so that a north pole faces a south pole across a gap of about 1.5 cm; the two sides should pull towards each other.
Mount the stand and pivot so a pendulum's plate passes through the middle of the magnet gap at the bottom of its swing without touching.
Pull the plastic plate back to 45° and release it. Count the swings and time how long it takes to stop: the magnets have almost no effect.
Repeat with the solid aluminium plate: it slows sharply and almost stops in the gap, because eddy currents in it oppose its motion.
- Repeat with the slotted plate
It swings much longer, because the slots break up the loops the eddy currents need.
Hold the pipe upright over a soft cloth and drop a magnet through it, then the plastic plug. Time both falls: the magnet falls far more slowly, although the pipe is not magnetic.
Make a results chart of swings, stopping times and fall times, and label uses such as train brakes and induction cooktops.
Read this first
Safety first
Go through these points before you build or switch anything on. Younger students should do this with an adult.
- Handle neodymium magnets carefully: they snap together hard enough to pinch skin and can chip, so slide them apart instead of pulling.
- Keep the magnets away from phones, bank cards and anyone with a pacemaker, and out of reach of young children, as swallowed magnets are very dangerous.
- Only an adult should cut the aluminium; file sharp edges and corners before handling the plates.
- Drop the magnet through the pipe over a soft cloth so it does not shatter on a hard floor.
Troubleshooting
If something does not work
The usual problems with this model and how to fix them. Open a problem to see the fix.
The aluminium plate is hardly slowed
The magnets may have like poles facing, which weakens the field in the gap, or the gap may be too wide. Turn one pair over so the two sides attract, and bring them closer.
The plate sticks to the magnets
The plate or arm contains iron or steel. Check with a magnet: aluminium is not attracted. Use a genuine aluminium sheet and a wooden arm.
The magnet falls quickly through the pipe
The pipe may be plastic or much wider than the magnet, or the magnet may be weak. Use a copper or aluminium pipe that fits closely round the magnet, or stack two magnets.
The slotted plate stops as quickly as the solid one
The slots are too short. Cut them deeper, almost to the top edge, so the current loops are properly broken.
Exhibition day
How to present it
A running order for the exhibition table or the practical, step by step.
Explain Lenz's law first, then show the effect on the board.
Describe the magnet falling slowly through a copper pipe as a simple extra example.
Explain why transformer cores are laminated to reduce eddy current losses.
Link the idea to the induction cooktop at home.
Practice
Viva questions
Practice questions on this model, with short answers. Try each one aloud before you open the answer.
What are eddy currents?
Circulating currents induced inside a conductor when the magnetic flux through it changes.
Which law gives the direction of eddy currents?
Lenz's law: they flow so as to oppose the change in flux that produces them.
How are eddy current losses reduced in transformers?
By making the core from thin, insulated laminations, which break up the paths of the currents.
Give two uses of eddy currents.
Induction cooktops and electromagnetic brakes; induction furnaces also use them.
Project file
Project file outline
The headings of the project file, in order. Give each heading its own section and write it in your own words.
Free ebook: Writing a Science Project FileContents
- Aim: to show eddy currents and how they oppose motion
- Introduction: electromagnetic induction in solid conductors
- Theory: Faraday's law and Lenz's law applied to a moving metal plate
- Construction of the magnetic pendulum and the falling-magnet pipe
- Observations: swings and stopping times for the plastic, solid and slotted plates
- Observations: fall times of a magnet and a non-magnetic plug through the pipe
- Why slots and laminations reduce eddy currents
- Applications: train brakes, induction cooktops, metal detectors and laminated transformer cores
- Conclusion and bibliography
Buying checklist
Before you buy
What to check before you order the model, and what to do when it arrives.
1Before you order
- Check that electromagnetic induction is in your syllabus at your class level, as eddy currents are usually taught in the senior classes.
- Read the listing to see how the board shows eddy currents and what powers it, and arrange anything extra in advance.
- Practise explaining Lenz's law in one or two sentences, as examiners usually ask why the plate slows down.
- Keep the box, and keep any magnets wrapped and away from phones in transport.
- Check the delivery date for your PIN code on the marketplace, and order well before the exhibition or practical.
2When it arrives
- Try the demonstration as soon as it arrives and again a few days before the exhibition.
Next steps
Take it further
Ways to turn this model into a bigger investigation or a stronger exhibition entry.
Replace the magnets with a battery-powered electromagnet and show a brake that can be switched on and off, as in electric trains.
Time a magnet's fall through copper and aluminium pipes of the same size and relate the difference to their conductivity.
Measure fall times for one, two and three stacked magnets and explain the results.
Audience
Who it suits
Class 12 physics students and engineering learners studying electromagnetic induction.
- SubjectPhysics
Free to read
Free ebooks for this topic
Free PDF ebooks from Gurukul Technicals Institute on the science, the making and the presenting of projects like this one.
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Physics Working Models Explained
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Your Science Exhibition Guide
Choose a project, build it, present it and answer the judges with confidence
- Free PDF ebook
Writing a Science Project File
How to write the report, from the cover page to the bibliography
