Can you demonstrate EM induction with a transformer and magnet?

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Discussion Overview

The discussion centers around effective demonstrations of electromagnetic induction for high school students, exploring various laboratory activities and experiments that can illustrate the concept. Participants share ideas and experiences related to using transformers, coils, and magnets in educational settings.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant suggests using toroids to compare magnetic field strengths in different materials as part of a broader exploration of induction.
  • Another participant proposes the "jumping ring" demonstration or a simple transformer as potential demonstrations.
  • A participant shares a detailed account of a demonstration involving a coil of magnet wire and a neodymium magnet, describing the steps taken to engage students with sound production through electromagnetic induction.
  • There is mention of using a giant classroom milliammeter and a demountable transformer to demonstrate induced EMF when a magnet is moved near a wire, emphasizing hands-on learning through small transformers and turns ratio exploration.

Areas of Agreement / Disagreement

Participants generally agree on the value of hands-on demonstrations for teaching induction, but multiple competing ideas and approaches remain regarding the best methods to achieve this.

Contextual Notes

Some limitations include the need for specific equipment like transformers and milliammeter, as well as the potential for varying student engagement based on the demonstration chosen.

Who May Find This Useful

Educators and instructors looking for innovative ways to teach electromagnetic induction in high school science classes may find these discussions and suggestions beneficial.

JFS321
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Hey folks, I'm looking for a high school laboratory to introduce students to induction. I've searched the usual suspects...Google, YouTube, etc...but nothing has really jumped out. I've ordered some toroids so students can compare the strength of magnetic fields in air versus ferrite, and I'll probably have them create an electromagnet, too. But, none of this really hits at the heart of induction. Any good demonstrations or ideas are much appreciated.

Joe
 
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How about the classical "jumping ring" demonstration? Or a simple transformer?
 
Last edited:
Thanks. I like the transformer idea; hadn't considered it. I'll do some searching.
 
http://www.exploratorium.edu/afterschool/activities/docs/cupspeaker.pdf

I did something like this using a tiny coil of "magnet wire" (thin coated copper wire) as a demo for my class


I did the demo gradually.
  • First... show that the magnet wire [not connected to anything] is not attracted to a magnet.
  • Next, over a small neodymium magnet, position a very light coil (connected to a boombox speaker output) supported by magnet wire leads.
    You can see it vibrate when the current in the coil is changing and the magnet is positioned correctly.
  • Then, I place a little piece of scotch tape to cover the coil... essentially, a membrane to push the air better.
    You can hear it if you place your ear near and the boombox output is high enough.
  • Then, I tape it to the bottom of the styrofoam cup... and get a louder sound, similar to that video.
I think students appreciated it.
I might turn it into a lab activity for them to build next time.
This "train" is pretty cool... but I couldn't get it to run like the video.

(I just found this set of instructions... . I might try again soon.)
 
Fantastic video and will make a great inquiry...it will be interesting to see if any of the students can determine what is happening. Thanks for the link!
 
JFS321 said:
Hey folks, I'm looking for a high school laboratory to introduce students to induction. I've searched the usual suspects...Google, YouTube, etc...but nothing has really jumped out. I've ordered some toroids so students can compare the strength of magnetic fields in air versus ferrite, and I'll probably have them create an electromagnet, too. But, none of this really hits at the heart of induction. Any good demonstrations or ideas are much appreciated.

Joe
You can demonstrate EM induction using the primary coil of a big transformer and a magnet. I use a giant classroom milliammeter. We also have a demountable transformer, and we can make small transformers using C-cores, with about 30 turns of wire, so the pupils can find out about turns ratio. We use 1 volt AC so it does not get hot. We also have a mirror galvo, so we can show an induced EMF in a wire when a magnet is passed near it.
 

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