Wednesday, 1 July 2015

voltage - Does current flow on an open transmission line?


Please take a moment to look at the diagram below:


enter image description here


The question is if the lightbulb will momentarily flash when the switch is closed. I think it will but I get the feeling I am wrong.


The reason why I think it will flash is because when the switch is closed, the transmission line wire electric potential should become the same as the electric potential found on the battery terminal and in order for that to happen, electrons will need to flow through the wire until electric potential balance is reached. As electrons flow through the wire, they will need to go through the light bulb filament causing the light to turn on.


By the way, I realize that the light bulb will not light up a room or that it will even light up at all, I am only using a light bulb here to illustrate my question and not mean to represent some sort of real life experiment.


Thanks.



Answer



Yes, there will be a brief pulse of current through the bulb as the portion of the transmission line (i.e., its capacitance) to the right of the bulb charges to the supply voltage.



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