The drift speed of electrons in a conductor is estimated to be only a few mm $s^{-1}$, But on closing a circuit, how current is established almost instantly in an electric circuit?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Electric field is established throughout the circuit with the speed of an electromagnetic wave, causing at every point local electron drift causing current.
The electric field propagates with the speed of an electromagnetic wave, not the drift velocity of electrons. The drift velocity $(v_d)$ is much slower than the propagation of the electric field, but it results in a continuous flow of charge, maintaining the current.