Question

A steady current flows in a metallic conductor of non-uniform cross-section. The quantity/quantites which remain constant along the length of the conductor is/are

• A. current, electric field and drift speed
• B. drift speed only
• C. current and drift speed
• D. current only

Answer 1

The correct option is D current only

Current in a wire is given by,
$i=neA{V}_d$

Here $n$ and $e$ are constants & for a given wire $i$ also remains constant.

$\Rightarrow A\propto \frac{1}{V_d}$

So, if $A$ changes $V_d$ will also change

Now, Electric field $E$ is given by,

$E=\frac{i}{\rho A}$

$\Rightarrow E\propto \frac{1}{A}$

So, if $A$ changes, $E$ also changes.

Hence, option ($d$) is the correct answer.