MCQ
When the current $i$ is flowing through a conductor, the drift velocity is $v$. If $2 i$ current is flowed through the same metal but having double the area of cross-section, then the drift velocity will be
- A$v / 4$
- B$v / 2$
- ✓$v$
- D$4 v$
✓
Answer
Correct option: C.
$v$
$ v_d=\frac{J}{n e} \Rightarrow v_d \propto J \quad \text { (current density) }$
$ J_1=\frac{i}{A} \text { and } J_2=\frac{2 i}{2 A}=\frac{i}{A}=J_1 ;$
$ \therefore\left(v_d\right)_1=\left(v_d\right)_2=v$
$ J_1=\frac{i}{A} \text { and } J_2=\frac{2 i}{2 A}=\frac{i}{A}=J_1 ;$
$ \therefore\left(v_d\right)_1=\left(v_d\right)_2=v$
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