User talk:61.68.50.51

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[edit] Question on transformer diagram

Hi, I have a question on the excellent diagram you made: http://en.wikipedia.org/wiki/Image:Transformer3d_col3.svg

Doesn't current flow from positive to negative? Why does the arrow on the secondary winding point outwards from the positive end if so? I'm only learning about transformers atm so forgive me if I'm making a silly error. 61.68.50.51 (talk) 05:44, 26 March 2008 (UTC)

Thanks for your message! Yes, the current does flow from positive to negative. Imagine placing a resistor between the two blue terminals on the right side. The current in it will flow from top to bottom, from positive to negative, and so in the same direction as it is drawn. The 'from positive to negative' convention is current flowing from the terminals of a voltage source, within the source the current is, so to speak, in the other direction. Consider a simple circuit, like this one, supplied by a battery. Current flows from the positive terminal, round the circuit and back into the negative terminal. But which direction does current flow within the battery? I hope this helps, but feel free to drop me another note if I didn;t explain it clearly enough. Regards, — BillC talk 08:59, 26 March 2008 (UTC)
I must admit I'm still confused - what exactly is the arrow indicating is moving? Also, why is the current inside the voltage source going in the opposite direction, wouldn't it just be a continuous flow? Thanks for taking the time to explain! I feel like I'm missing something elementary here... 61.68.50.51 (talk) 09:16, 26 March 2008 (UTC)
The arrow is indicating the direction of conventional current flow. The flow of current is a continuous flow around the circuit, it is not going in the opposite direction inside the source. I don't think I have been very clear in my explanation: by the 'other direction', I meant within the source it is flowing into the negative terminal and from there to the positive. I think you answered your own question in its second sentence. The secondary winding of the transformer acts as a voltage source (and the primary as a load). Try drawing a secondary winding of a transformer with a resistor connected across its terminals. Mark one terminal as positive and then draw the direction of current flow. You will see it is the same as the image. — BillC talk 19:05, 26 March 2008 (UTC)
"The secondary winding of the transformer acts as a voltage source (and the primary as a load)." Ah! Makes perfect sense now - I was thinking of a source being between the two ends of the wire for some reason. Thanks very much. :) 61.68.50.51 (talk) 07:18, 27 March 2008 (UTC)