Induction Experiment - Magnetic Field through a Toroid

nbsmith

I want to build a simple induction apparatus like the one displayed at this web page: http://micro.magnet.fsu.edu/electromag/java/faraday/

My first attempt didn't work, and I'm trying to troubleshoot it. I am wondering how much magnetic field degradation there is around the toroid. As the switch is closed and a magnetic field is created, how strong is the magnetic field by the time it gets to the other solenoid on the other side of the toroid? It could be that nearly all of the field strength is preserved around the toroid, or it could be that it is much weaker on the other side.

Does anyone have any idea how much the field degrades around the toroid? Perhaps this apparatus works in principle, but is not very efficient in practice.

Thanks.

bjacoby

Um, I hope you noticed that in the description of the apparatus that the toroid was made of "soft iron"! That is the key as to why there is no field degradation from one side to the other. Other materials, for the most part, won't work. With just air coils the thing will be quite inefficient. OK?

nbsmith

I was using a ferromagnetic metal toroid, but it wasn't soft iron. Would the magnetic field travel around that without much degradation?

Antiphon

It should work. You are looking for a tiny deflection of the needle only when you
open or close the switch. There is no deflection when the switch stays open or
stays closed.