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In Example 3.1. the electron drift speed...

In Example 3.1. the electron drift speed is estimated to be only a few mm `s^(-1)` for currents in the range of a few amperes ? How then is current established almost the Instant a circuit is closed ?

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When a battery is connected across a conducting wire, electric field is found to be established in that wire almost with a speed of light. This causes instantaneous local drift of every free electron and that too with a tremendous acceleration because its value
given by a = `(eE)/(m)` is found to be very large (because m being mass of electron is extremely small equal to `9.1 xx 10^(-31) `kg)
Hence all the free electrons start drifting simultaneously which produces instantaneous current in the wire. This current achieves its steady value within a very short time. (That is why bulb gets on almost at the same moment when we switch it on).
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