Question

Two wires $A$ and $B$ of the same material, having radii in the ratio $1:2$ and carry currents in the ratio $4:1$. The ratio of drift speed of electrons in $A$ and $B$ is

• A. $16:1$
• B. $1:16$
• C. $1:4$
• D. $4:1$

Answer 1

The correct option is A $16:1$

Current flowing through the conductor, $I=nevA$.

Hence
$\frac{4}{1}=\frac{ne{v}_{d_1}\pi (1{)}^2}{ne{v}_{d_2}(2{)}^2}$

or

$\frac{v_{d_1}}{v_{d_2}}=\frac{4\times 4}{1}=\frac{16}{1}$

Hence correct answer is option A.