Question

A polythene piece rubbed with wool is found to have a ‒ve charge of 3 × 10–7 C.

(a) Estimate the number of electrons transferred (from which to which?)

(b) Is there a transfer of mass from wool to polythene?

Answer 1

Given,

q = -3 × 10-7 C on polythene

Charge on polythene is negative so electrons are transferred from wool to polythene.

(a) q = ne

Since, e = 1.6 × 10-19 C  

Therefore, n = |q|/e = 1.875 × 1012 electrons.

1.875 × 1012 electrons are transferred from wool to polythene.

(b) Yes mass is transferred as electron has a mass of 9.1 × 10‒31 kg.

Total mass transferred

= number of electrons transferred × mass of an electron

= (1.875 × 1012) (9.1 × 10‒31) = 1.7 × 10‒18 kg.

Answer 2

Hello friends.

(a) We know, electric charge of a body is quantized

e.g., Q = ne

Given, Q = 3 × 10⁻⁷C

e = 1.6 × 10⁻¹⁹ C [ charge on each electron ]

n = Q/e = 3 × 10⁻⁷/1.6 × 10⁻¹⁹

= 3/1.6 × 1.875 × 10¹²

So, 1.875 × 10¹² electrons have transferred from wool to polythene .

(b) yes , as you know, mass of electron = 9.1 × 10⁻³¹ kg

∴ transfer of mass = number of electron × mass of each electron

= 1.875 × 10¹² × 9.1 × 10⁻³¹

= 1.71 × 10⁻¹⁸ Kg has transferred from whool to polythene.

hope it's helpful for you...

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