Question

The drift velocity of electrons in a conducting wire is of the order of $1mm/s$, yet the bulb glows very quickly after the switch is put on because

• A. the random speed of electrons is very high of the order of ${10}^{-6}m/s$
• B. the electrons transfer their energy very quickly through collision.
• C. electric field is set up in the wire very quickly, producing a current through each cross section, almost intantaneously
• D. All the above

Answer 1

The correct option is C electric field is set up in the wire very quickly, producing a current through each cross section, almost intantaneously

Drift velocity $v_d=\frac{eEt}{m}$ so drift velocity is directly proportional to the electric filed. When switch is on, the filed is quick set up wire and produce current through wire instantaneously.