| ASSERTION: If the length of the conductor is doubled, the drift velocity will become half of the original value (keeping potential difference unchanged). |
| REASON: At constant potential difference drift velocity is inversely proportional to the length of the conductor. |
A) If both assertion and reason are true and reason is the correct explanation of assertion.
B) If both assertion and reason are true and reason is not the correct explanation of assertion.
C) If assertion is true but reason is false.
D) If both assertion and reason are false.
E) If assertion is false but reason is true.
Correct Answer: A
Solution :
Drift velocity of free electrons is given by \[{{v}_{d}}=\frac{eE}{m}\tau \] Where \[E=\frac{Potential\,difference}{length}=\frac{V}{l}\] \[\therefore \,\,{{v}_{d}}=\frac{eV}{ml}\tau \] i.e. \[{{v}_{d}}\propto \frac{1}{l}\] where \[\frac{eV\tau }{m}\] is constant. it mean if l is doubled, the drift velocity will become half of the original value.
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