Question

A potential difference V is applied to a conductor of length l and diameter D.How are the electric field intensity E ,drift velocity V_d and the resistance R affected when
(i)V is doubled
(ii)I is doubled and
(iii)D is doubled?

Answer 1

Given,

Potential difference = V

Length of the conductor = I

Diameter = D

Electric field intensity E = $\frac{V}{l}$

So, When V is doubled E will also be doubled

When l is doubled E will be halved

Drift velocity is given as $v_d=\frac{eEt}{m}$

When V is doubled E will be doubled and so drift velocity will also be doubled

If l is doubled E will be halved and so drift velocity will also be halved

Resistance of the wire is given as $R=\text{ρ}\frac{l}{A}$

If l is doubled then the resistance of the wire will also be doubled

If D is doubled then the area becomes four times and so the resistance becomes one-fourth.