Question:
The electron drift speed is estimated to be only a few
mm/s for currents in the range of a few amperes.
How, then, is the current established almost the
instant a circuit is closed ?
The electron drift speed is estimated to be only a few
mm/s for currents in the range of a few amperes.
How, then, is the current established almost the
instant a circuit is closed ?
Updated On: Jul 2, 2026
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Solution and Explanation
Although the drift velocity of electrons is very small (only a few mm/s), the electric field produced by the battery is established throughout the conducting wire almost immediately after the circuit is closed.
This electric field propagates through the circuit nearly with the speed of light. As soon as the field reaches the free electrons present everywhere in the conductor, they start drifting simultaneously.
Thus, the current appears almost instantaneously throughout the circuit, even though an individual electron moves very slowly.
Therefore:
- The electrons do not travel from the battery to the bulb instantly.
- The electric field is established almost instantly.
- All free electrons in the conductor begin drifting at the same time, establishing the current immediately.
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