Current is a flow of electrons within a conductor. Lets assume that there is cir

Question

Current is a flow of electrons within a conductor. Lets assume that there is circuit that runs from here to San Antonio, which contains a light bulb located at San Antonio. Once this circuit is connected to a power supply current is recorded and the light bulb produces light. Once the circuit is closed the light bulb will light up instantaneously.

The question is this: Do electrons located at Edinburg will travel to San Antonio for the light bulb, located at San Antonio,  to operate ?  In general in case of electrical current within conductors do electrons physically move AND travel along the wire for long distances fast? Please explain your reasoning without the use of mathematics.

Explanation / Answer

The electrons do physically move when the bulb is switched on. But the transfer of energy is not due to the movement of electrons. If it were so then the bulb will not glow instantly since the drift velocity for electrons is extremely low.

Instead, the charges get induced inside the wires due to potential difference now applied (which is the switched on power supply). This gives rise to an electric field which transfers the energy across the circuit at around the speed of light. The energy is stored in the electric field and its propagation gives the energy transfer thus lighting the bulb, not the propagation of electrons.

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