Question

A current flows in a wire of circular cross-section with the free electrons travelling with a mean drift velocity v. If an equal current flows in a wire of twice the radius new mean drift velocity is

• A. v
• B. $\frac { v } { 2 }$
• C. $\frac { v } { 4 }$
• D. None of these

Answer 1

Answer: (C)

$\frac { v } { 4 }$

Answer 2

By using $v _ { d } \propto \frac { 1 } { A }$ ⇒