Question

(a) Explain the term drift velocity of electrons in a conductor. Hence obtain the expression for the current through a conductor in terms of drift velocity.

(b) Two cells of emfs E₁ and E₂ and internal resistances r₁ and r₂ respectively are connected in parallel as shown in the figure.

Deduce the expression for the

(i) equivalent emf of the combination

(ii) equivalent internal resistance of the combination

(iii) potential difference between the points A and B.

Answer 1

(a) Drift velocity: It is the average velocity acquired by the free electrons superimposed over the random motion in the direction opposite to electric field and along the length of the metallic conductor.

Derivation I = ne A V_d

(b) Here, I = I₁ + I₂   ...(i)

Let V = Potential difference between A and B.

Comparting the above equation with the equivalent circuit of emf ‘ε_eq’ and internal resistance ‘r_eq’ then,