Can you demonstrate EM induction with a transformer and magnet?

[JFS321]

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

 

[deskswirl]

How about the classical "jumping ring" demonstration? Or a simple transformer?

 

[JFS321]

Thanks. I like the transformer idea; hadn't considered it. I'll do some searching.

 

[robphy]

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.)

 

[JFS321]

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!

 

[tech99]

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.