(a) nearly 
m/s
(b) of the order of a few µm/s
(c) independent of current strength
(d) same as propagation velocity of electric energy
Correct Answer: (b) of
the order of a few µm/s
Explanation
Electron drift velocity is
extremely small, though electrical signals propagate almost at the speed of
light.
Notes for
More Information
Current Velocity in a Copper Conductor (Drift Velocity)
- The current velocity in
a copper conductor is called the drift velocity of
electrons.
- Drift velocity is the average
speed at which electrons move through a conductor due to an
applied electric field.
Actual Electron Motion vs Signal Speed
- When voltage is
applied, electrical signals and energy travel very fast through
the conductor.
- This signal speed is
close to the speed of light.
- However, the electrons
themselves move very slowly.
- The slow movement of
electrons is what we call drift velocity.
Magnitude of Drift Velocity
- In a typical copper
conductor, the drift velocity of electrons is extremely small.
- It is of the order
of a few micrometers per second (µm/s).
- Numerically, drift
velocity usually lies between:
- 10⁻⁴
m/s to 10⁻³ m/s
- That
is approximately 0.1 mm/s to 1 mm/s
- The exact value depends
on factors such as:
- Cross-sectional
area of the wire
- Magnitude
of current flowing
Important Clarification
- Drift velocity is not
the speed of electricity.
- It only represents the
slow movement of electrons.
- The propagation
speed of electrical energy is much higher, typically 50%
to 99% of the speed of light.
Conclusion
- Since electron drift
speed is extremely small, the correct answer is:
- (b) Of the order of a
few µm/s
