Question

a conductor of length L is connected to a d.c source of emf E. If the length of the conductor is tripled by strectching it, keeping E constant, explain how it's drift velocity will be affected.

Answer 1

Answer:1/3

Explanation:As the E is V/L therefore putting this value in the drift velocity expression will tell us how velocity is inversely proportional to length.

Answer 2

Answer:

If the length is increased n times the drift velocity decreased to 1/n.

Explanation:

CONCEPT:

• Drift velocity(V_d) :The velocity in which the free electrons can be drifted towards the positive terminal under the effect to the applied electric field.

        $&v_{d}=\frac{I}{n e A}=\frac{V / R}{n e A}=\frac{V /(\rho L / A)}{n e A}=(\because R=\rho L / A)$

• n= number of electrons ,V= voltage applied, e= charge, A= area of cross section, L= length of wire, R= resistance of wire.

EXPLANATION:

                                       $v_{d}=\frac{V}{n \rho e L} \\{ or } \\v_{d} \propto \frac{1}{L} \\\\\therefore \frac{V_{d}^{\prime}}{V_{d}}=\frac{L}{3 L}=\frac{1}{3} \\\\\text { or }\\ v_{d}^{\prime}=\frac{v_{d}}{3}\end{aligned}$

• Where v'd= drift velocity when the length is tripled.
• When the length is tripled the drift velocity becomes one third of actual drift velocity.

If the length is increased n times the drift velocity decreased to 1/n.