When winding an inductor and you reach the end of the other side, do you jump the wire across to the beginning and continue winding or can you continue to wind from the other side to the beginning for the second layer of wire? Would there be cancellation of the inductance value. I want to make a choke for an Radio Frequency oscillator. It's hard to make my question clear.
Would there be cancellation of the inductance value
Picture the current in a single turn of wire. Let's say the current is 1 amp travelling clockwise at a particular moment in time. If you have two turns wound the same direction, then the currents in each wire are both travelling clockwise.
You have created a magneto motive force (MMF) of 2 ampere-turns with those two wires each carrying 1 amp. That MMF could equally have been created with 1 wire carrying 2 amps or a thousand wires carrying 2 mA. The magnetic field produced would be identical.
Now, if you picture one turn carrying current counter-clockwise, its magnetic field would cancel one turn carrying the same current in a clockwise direction.
So, providing the currents are all travelling in the same direction around a common centreline then there will be no cancellation of either magnetic field or inductance.
As long as you keeping winding the wire the same way round the cylinder, it doesn't matter whether you wind the first layer up and the second back, or the first up, send the wire straight back to the first end, and then wind the second layer up as well.
Most people wind up and back, but there is a subtle advantage to winding only up, retracing the wire between layers. The self capacitance of a coil wound this way will be a little lower, and so the self resonant frequency will be a little higher. This method is rarely used however, as if self capacitance is important, there are other winding arrangements which work even better to minimise it.