I was just reading Electric Power Engineering by Elgerd when I came across these statements about flux I couldn't fully understand:
- "By experiment, we can confirm a most interesting characteristic of the flux. If we keep the iron core position fixed but move the cable to any position inside the core window, the flux will not change. (The reader should contemplate what happens to the flux in the air core under the same conditions.)"
Why is this so? Shouldn't changing position increase flux in the regions of the core close to it and decrease in the far away areas? Is this the case for air core?
- "The flux will not change even if we bend the cable into any conceivable shape as long as the total current Ni remains unchanged and as long as it passes through the core window. In fact, the magnetic flux will remain unchanged if we replace the N-strand cable with an N-turn coil carrying a current i as long as the product Ni stays constant."
I have trouble imagining what the N-turn coil he's referring to would be placed like. Wouldn't it cause NI going in and coming out both?
Also, what would happen if I change the shape of the iron core itself keeping the cable straight? How would flux change then?