Monday, 5 January 2015

basic - If Conventional Current is wrong, how can I trace the flow of current in a schematic?


If Conventional Current is backwards, how do I look at something like this schematic and trace the flow of current? I'd like to follow the design linearly from positive to negative.


enter image description here


When the battery is on, does current go to 8, then 4, then through R1 and so on?


Does the current get "back around" to the side of the capacitor, 1, and the speaker eventually (though fast)?


How can this be so if in reality electrons flow from negative to positive?


Edit: If the current were water here, how would I see that physically on the wiring, as if they were pipes?



Answer



Conventional current being backwards from electron flow has no effect whatsoever on circuit analysis. If you really wanted, you could swap the signs on all your currents and voltages and the math would work out the same, but people would be confused.



If you're doing an ad-hoc intuitive analysis without any math, well, it still doesn't matter whether you start at the positive end or the negative end of things, or neither.




The behavior of currents flowing in wires and through components can and should be be understood symmetrically — positive and negative voltages/currents, or electrons and “holes”, being equal and opposite to each other.


The causality, the ways changes propagate around a circuit, is also symmetric. If you close a switch or make some other such change, the changes in voltage and current propagate away from the switch along both connected wires — with opposite signs, but otherwise completely identical, at the same speed.




Specific components (diodes, ICs, capacitors, tubes…) may have polarity, so they require or only allow a flow with a specific direction/sign, but it does not actually matter at all for understanding the behavior of the circuit which one matches the actual flow of electrons — only if you want to understand why the components do what they do does that begin to matter.


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