# Re: [TCML] BIGPIG secondary dies...but may be resurected

I think Ed is correct. According to models, the larger the top load is relative to the coil size, the "less" the current changes from top to bottom. But if a bare coil, it is max to zero (or near). Also, the linearity of the distributed current along the length of the coil is dependent on the h/d (more linear for low h/d coils).
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For the normal h/d of 4 or 5, it's not quite linear, but curved even with bare coils. Throw a big toroid on the coil and the current is far less changing from bottom to top because the toroid is very well adapted at forcing itself (it's C imposed on the inter C of the windings) and changing the overall distributed capacitance of the coil due to the toroid geometry. The current as a result becomes less changing from bottom to top (but there is still a difference). So no, current is not the same from end to end from a technical stand point. And it can never be the same unless you throw turn to turn C out of the equation.
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If you make a statement as "the top current is smaller than the bottom current", then you would be correct. The problem is the person stating this usually does not know "how much smaller". In rare cases, it can be a lot. In most TC cases, it's not a big change. If I were to give a "number", I would say the current on average coils is about 25% less at the top than it is at the base. But, that's just truly rough guesstimate of what I would call average coils and average tops to coils size.
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Take care,
Bart

Ed Phillips wrote:
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It's a long piece of wire with capacitance between turns and capacitance of each turn to the surroundings. Current distribution depends on how much top load capacitance is on the coil. With no top loading the current will be lower at the top; if there are no streamers the current should be essentially zero at the top. Distributed capacitance is the culprit.
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Ed

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