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Hi electricpete! First of all, I want apologize if my English is not very good or it seems not polite... I'm italian!!! Thank you all for your comments and I apologize for my insistence... but I like to understand and be convinced. Far from me to think that Zhan (but also you) may be mistaken...

Sorry... but this time I don't agree... I don't speak about voltage in one or more turns... The Area is changing beacuase the formula and the experience say that if in one turn of area A (omissis...) the flux is BxA, if we have N turns of the same area, the flux is NxAxB... Your explanation...

Hi!!!! Then.... reassuming.... If I well understood, the emf will be 0 beacuase there are not moving electrons using switch (instead, moving side of the circuit there are!)... I have electrons inside the moving wire (they are subjected to a force deriving from B field e v of the side) that I...

Hi IRstuff... How I said at the beginning, this is only to make toy to my granddaughter [bigsmile] I started with normal dinamo (coils and magnet tourning inside... easy to do and easy to see on the oscilloscope) (B variant) and then I have moved to change area... and that was the problem and...

Sorry, but (if I have well understood what a "center-tapped transformer" is) there is not inversion of flux on it. All the concept is based on clocck-wise and counter-clockwise turn of coils... that varies the total area of the spiral

Another concept: I don't "create" nothing!!! I spend work to move the switch, then it is possibile that I obtain emf from that work

Good w.e. to all of you! :-) I try to better explain my logic (?... confusion, mistake???? ) I know that moving Test Point along a spiral does not generate emf (in this case we move only measuremnt point but A and B remain constant!) With reference to the fig.6.5 (pag.400) we can see that, in...

Thanks for your comment. Sorry, I can't answer now (I'm out of home). I will ansewr and try to explain better my problem (and confusion) on saturday.

Sorry, I didn't understand these sentences: "If break before make switch, voltage is zero before and after the swap. If make before break switch (doesn't mattter,not currrent is flowing), would be zero before during and after the switch." Anyway, a Voltmeter doesn't show nothing. The emf is...

Hei... one step at the time!!!! This is the second step!!! [bigsmile] The first step is: "Is the formula valide?".... if yes, we can go haed on the second step: "How?"... At the moment we can suppose (this is real situation till now!) use a tumbler electrical switch ("current reverser", I think...

Thanks... I know that typically N and, sometime, A are fixed... this is why i'm asking to the forum [bigsmile] I'd like to vary only N, not A. Then the formula should be emf = AB d(N)/dt And, because the change is as step function, I should have an impulse as emf. I tried with due coils (of...

Morning. I would like to speak about the EMF induced by a magnetic field in a coil. I refer to the formula fem = d(NAB)/dt In all texts is always something about an A or a B variable with the time, but nothing about N. I would like to know if above mentioned formula is still valid in this...