Though the drift velocity of electorn responsible for current in a conductorn under ordinary circumstances is very small, light in a room turn on immediately after the swithc is closed, Explain why and how?

Explanation

When switch is made on, the electric field `vecE` responsible for
setting current is transmitted through the wire from swithc
to bulb at speed of light `c =3xx10^8ms^(-1).` So in time L/c, i.e.,
immediately after the field is set up in the circuit, electrons start
drfting producing current and hecne light. However, the electron
at the switch will take time `L/v_d, i.e.,` hours to reach the bulb if
it reaches the bulb at all.