1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Why does number of coils on primary affect frequency?

  1. Feb 25, 2016 #1
    I'm reading a guide on how Tesla coils and slayer exciters work on this Instructable and it was speaking about how to fine-tune the Tesla coil in order to match the resonant frequency of the secondary coil. I understood it when it spoke about changing number of capacitors or the distance of the spark gap (for SGTCs), but I don't see how adjustment of number of coils on the primary affects the resonant frequency of the primary, allowing you to match it with that of the secondary. I'll put a short quote down below from the link I put up top that seems to sum up what he says about adjusting primary coil number to change frequency.
    I'm confused because that way I understand is that the frequency is mainly based on how often the capacitors fire off, so I don't see how adjustment of number of coils in primary can change how often electricity goes through the primary, since the capacitors fire off independent of that, right?
  2. jcsd
  3. Feb 25, 2016 #2


    User Avatar
    Homework Helper
    Gold Member

    No, the capacitor discharging frequency is much too low. The resonant frequencies are typically millions of cycles per second, but the sparks are likely to be typically up to tens per second. Each spark causes many cycles of oscillating current in the pimary, with energy being slowly transferred to the secondary until the current is too small to sustain the arc. Then charge (and stored energy) builds up on the capacitor until the next spark.

    Coil and capacitor circuits have a resonance determined by the inductance of the coil (related to the number of turns) and the capacitance.
    An analogy is sometimes made with a mass on a spring. The capacitor is like the spring and the inductance is like the mass. If the mass is made smaller (like a coil having fewer turns) it vibrates more quickly, or made bigger (more turns) it vibrates more slowly.

    You probably need to look up LC circuits or radio frequency "tank" circuits. (L stands for inductance or coil, C for capacitance.)
  4. Feb 25, 2016 #3
    Thanks, that was a pretty good explanation! I'll have to do some research on LC circuits, but what you said has made Tesla coil operation much more clear for me.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook