I have an induction setup that I have in the picture below: Induction

According to Faraday's Law, a changing magnetic field of a primary coil causes an instantaneous change in emf of the other coil. I have 60Hz AC from the variac so like a transformer, AC happens in all affected coils. I am lost though since the secondary coil does not have any AC. The primary connection is in series. I have tried to move the secondary coil closer to the first coil and I have tried using a magnetic core using neodymium magnets and I have tried using different light bulbs but to no luck. The following data that I have recorded is below.

Materials used are:

  • 13 AWG copper magnet wire
  • 2 light bulbs, the ones I have chosen are rated at 12W
  • Variac(AC power)
  • Alligator clips
  • Wooden Frame
  • Lightbulb screw-on case
  • Multimeter


  • 0.034A @ ~25VAC for the primary connection
  • Current increases as VAC increases
  • 0.2 ohm resistance on each coil
  • 1.5Mohm resistance on the lightbulb used in the picture
  • Continuity exists checking on the coils, variac, primary connections, and secondary connections.

Any help would be great!

  • 1
    \$\begingroup\$ Instead of explaining your project and stating that you need help identifying a problem, instead state: 1) What you expect/want to happen; 2) What is actually happening; 3) What you've tried so far; and 4) Ask a question that encapsulates what you do not know. \$\endgroup\$
    – JYelton
    Jan 6 at 16:58
  • 2
    \$\begingroup\$ I'm surprised you read nothing at all, but with at most 10 turns on each side and no magnetically permeable core I wouldn't have expected much anyway - particularly at 60Hz. "neodymium magnets" are no good as a transformer core, and whatever you use for a core really should be a continuous loop with no air gaps. \$\endgroup\$
    – brhans
    Jan 6 at 17:00
  • 1
    \$\begingroup\$ According to Faraday's Law, a changing magnetic field of a primary coil causes an instantaneous change in emf of the other coil. - incorrect. \$\endgroup\$
    – Andy aka
    Jan 6 at 17:19
  • \$\begingroup\$ You'll need many many many MANY more turns actually. Like measured in hundreds or thousands IMO. And the coils are WAYYYYYYY too far apart. And 13AWG is not a good wire... that's capable of around 10+ amps.. You are passing milliamps. Some 24AWG or so would be far more practical (you will get more turns for the same volume). \$\endgroup\$
    – Kyle B
    Jan 6 at 18:59
  • \$\begingroup\$ Be careful with that variac too brother... That is NOT ELECTRICALLY ISOLATED like a typical transformer would be. i.e. there's a direct wire connection STRAIGHT TO THE WALL OUTLET. Super easy to zap yourself even if you have it set quite low. \$\endgroup\$
    – Kyle B
    Jan 6 at 19:00

You have the light bulb and the primary coil in series. Because The whole voltage is probably across the bulb there is no voltage across the primary coil. If there is no voltage on the primary there can’t be voltage on the secondary. Also an air core transformer doesn’t work at 60Hz. Magnets can’t be used as a core. Try using a closed iron core like a typical transformer looks like. Or use a higher frequency if you want to use an air core. Also don’t have anything in series with the primary coil.

  • \$\begingroup\$ Yep that is definitely the case as the voltage is close to zero across the coil. However, just the coil alone will cause a short circuit as I have experienced so I will try a parallel circuit. Would an iron pipe work though at the center of each coil work as the core? \$\endgroup\$ Jan 6 at 17:29
  • 2
    \$\begingroup\$ @JuicyYellow you need to put many, many more turns on your primary if you're going to connect it to anything more than a couple of volts at 60Hz. An iron pipe would sorta-kinda work (it would be better than nothing), but you need to make sure you build a complete loop of it and not just a single straight pipe . \$\endgroup\$
    – brhans
    Jan 6 at 17:45

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