Question

In the absence of applied potential, the electric current flowing through a metallic wire is zero because

• A. the electrons remain stationary
• B. the electrons are drifted in random direction with a speed of the order of \(10^{-2}\) cm/s
• C. the electrons move in random direction with a speed of the order close to that of velocity of light
• D. electrons and ions move in opposite direction

Hint:

Without an electric field, electrons move randomly, so average velocity is zero and hence current is zero.

Answer 1

The Correct Option is B

Step 1: Motion of electrons without electric field.
In a metal, free electrons are always moving due to thermal energy.
Step 2: Random motion leads to zero net current.
Since their motion is random in all directions, the number of electrons moving in one direction equals those moving in opposite direction.
Thus, their average velocity becomes zero.
Step 3: No drift velocity without applied potential.
In absence of electric field, there is no preferred direction, so drift velocity is zero.
Step 4: Therefore net current is zero.
Hence current is zero even though electrons are moving randomly.
Final Answer:
\[ \boxed{\text{(B) random drifting gives zero net current}} \]