Coils at right angles

Hello everyone,

In my continuing pursuit of understanding of oscillator circuits, I came up with this question and was wondering if anyone here could give me some insight on this. I drew a picture to help me explain the idea but I would like to know what would happen if you have an inductor (air core solenoid for example) and you wrap a second coil around the first coil at 90 degrees to it. If the solenoid coil has an AC sine wave signal put through it, would the second coil experience induction in the same way as normal? If this solenoid coil were part of an oscillator, how would the presence of this second coil effect its operation (Particularly if a load is placed on it)? Would it change the resonant frequency of the oscillator circuit or simply dampen it?? I heard of someone who did a similar experiment and they say the second inductor produces pulsed DC... not sure though. Any help would be appreciated :-).

Jason O


Ohh one other note, the original experimenter who got the pulsed DC did not use coils at right angles, he took some small gauge wire and wrapped it around a lamp cord. He then ran a sine wave through the small coil and registered pulsed DC coming out of the lamp cord.


No, there would not be any flux coupling if the windings were done carefully. However, if the 2nd coil were pushed in a bit toward the center of the big coil (in your 2nd sketch), and the windings were tilted a bit, then I think you could get some net flux coupling. I don't know what your friend with the lamp cord was seeing, but it almost certainly wasn't from magnetic coupling. Lamp cord has both conductors in it, so wrapping a coil around both will not induce anything differential. He maybe got some capacitive coupling, or had an instrumentation problem.
If the coils are parallel, engineers always like to say they are talking to eachother.

If they are perpendicular, then the fluxes can't link together.
Hmmmm interesting. Thanks for the information :-).

The Physics Forums Way

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving