Question

When a Piece of Polythene is rubbed with wool, a charge of – 2 × 10^–7 is developed on polythene. The mass transferred to polythene is …. kg. 

(A) 11.38 × 10^–19 

(B) 5.69 × 10^–19 

(C) 2.25 × 10^–19 

(D) 9.63 × 10^–19

Answer 1

The correct option (A) 11.38 × 10^–19

Explanation:

Here number of electrons are transferred from wool to polythene.

amount of charge on polythene = – 2 × 10^–7­­ = q

amount of charge on electron = – 1.6 × 10^–19 = e

Let number of electrons transferred be n.

∴ n = (q/e) = [(– 2 × 10^–7) / (– 1.6 × 10^–19)]

∴ n = 1.25 × 10¹²

mass of vector e = m_e = 9.1 × 10^–31 kg.

hence mass transferred   = n ∙ m_e

= 9.1 × 10^–31 × 1.21 × 10¹²_­

= 11.38 × 10^–19 kg.