First of this is actually not a one question but 2. I know that the drift velocity of electrons is less than the pace os a snail but it's the Electric field that gives rise to the current instantaneously. I had the question that how come a field is set up in a wire. Regarding this I found these 2 fabulous answers Why doesn't the electric field inside a wire in a circuit fall off with distance from the battery?
1) Based on this I could make out that the field in the wire does not fall off with distance because there will be a build up of electrons in the bends or after a certain distance to increase the field. But I don't think this is absolutely right . I would like some one to elaborate more on this.
2) Based on this , could some one explain why does the potential falls across a resistor but remains constant in the wire. Everybody explains it in terms of loss of energy as heat leading to p.d. But I would like the explanation in terms of the field picture in sense of build up of charges across resistors like the above links.
Now to the question.
Considering the build up of charges , etc, how does a bulb (resistor) light up instantaneously. It should take a little time to get hot and glow. Is the process so quick or is there physics in it ? I just can't get how the bulb glows instantaneously ?