The drift speed is defined as v d = Δℓ/Δt where Δℓ is the distance drifted in a long time Δt. Why don’t we define the drift speed as the limit of Δℓ/Δt as Δt → 0?

Question

Philoid · Accepted Answer

Since an electron, during a drift, travels in a very random and discontinuous path, we have to take an average of the distances over a long interval of time, and since limiting ∆t ⇒ 0 corresponds to a very short time interval we don’t define drift velocity as such.

The drift speed is defined as vd = Δℓ/Δt where Δℓ is the distance drifted in a long time Δt. Why don’t we define the drift speed as the limit of Δℓ/Δt as Δt → 0?

The drift speed is defined as v_d = Δℓ/Δt where Δℓ is the distance drifted in a long time Δt. Why don’t we define the drift speed as the limit of Δℓ/Δt as Δt → 0?