Effects on inductance of opposite current direction in inductor
THX
Yes, it is reduced. If you could cancel out the H field completely, everywhere, at all times, then the inductance should be zero since energy is stored in the H field.
A standard method for making variable inductors is to have a copper slug whose position in a solenoid coil is adjustable.
No, i dont think so.
So if you wind a 2 layer solenoid with the 2nd layer in the opposite direction as the first layer, it will have the same inductance as a normal two layer coil?
No! but i think myem question was another thing.
Thanks for everyone's explicit feedback.
Allow me to show eazy picture to explain my question
You can see the opposite current direction in that.
What effect on opposite current direction ?
THX a LOT
Yes, that should reduce the inductance. Now it may not do it much unless you get the traces right on top on one another. You can use a linear simulator and coupled inductor model to see the effect, or use a planar EM simulator to plot inductance of a U shaped trace vs. spacing (keeping length constant), or you may be able to use an analytical model for coupled transmssion lines. See Bob Weber's book "Introduction to Microwave Circuits" to see how he derives mutual inductance between parallel bond wires.
In this case it should reduce the inductance as madengr said.
if you want to make this inductor on PCB, you can use somthing like this:
I'm now thinking what I stated before may only be valid for low frequencies. As the traces length becomes a significant fraction of a a wavelength then the time delay would not allow the the fields to cancel.