Science Buddies: "Ask an Expert"

I am helping my son build the spark gap induction coil he found on this website. We understand the concept between the primary & secondary coil.We have 12 wraps on our primary & the pvc pipe we used is 4 inches per 1 wrap. We plan on doing 9000 wraps. One problem we are having is getting the 5/8 inch carrage bolt to magnetize. We are applying both 6 volts & also 12 volts directly to the bolt. We insulated the bolt from the primary with shrink wrap. We can't get the Neef type vibrator to work if the bolt doesn't magnetize. Should the bolt be magnetized as long as the switch is closed? Should the windings on the primary be spaced apart or should they be touching each other? What is the best way to get the primary to work the neef type vibrator? Also is the type of bolt used important such as galvanized, stainless steel, or a soft iron bolt? we are using a stainless bolt . Is this why we may be having problems with this part of the experiment?

Hi there,

https://www.sciencebuddies.org/mentorin ... ?from=Home

In your description you state that : "We are applying both 6 volts & also 12 volts directly to the bolt...".
However in the diagram in the link above (project description) it does not show to apply a voltage to the bolt. Instead the bolt's purpose, if I got this right, is only to act as a mechanical interuptor to the neef vibrator. The bolt will swing left to right due the changing magnetic field caused by the primary and thus connect and disconnect the primary loop.

I would think you want a material that reacts in a magnetic field. Did you try to see if the bolt attaches to a normal magnet ?

Hope this helps.