Question

A glass rod is rubbed with a silk cloth. The glass rod acquires a charge of +19.2xx10^(-19)C.
(i) find the number of electrons lost by glass rod.
(ii) Find the negative charge acquired by silk.
(iii) Is there transfer of mass from glass to silk?

Answer 1

Given:

Charge acquired by the glass rod = +19.2 × 10⁻¹⁹ C

To Find:

(i) No. of electrons lost by glass rod.

(ii) Negative charge acquired by silk.

(iii) Transfer of mass.

Calculation:

(i) Electrons lost by glass rod = Charge acquired by rod/Charge on 1 electron

⇒ n = 19.2 × 10⁻¹⁹ / 1.6 × 10⁻¹⁹

⇒ n = 12

(ii) Negative charge acquired by the silk cloth = - (Charge acquired by the glass rod)

⇒ Negative charge acquired by the silk cloth = -19.2 × 10⁻¹⁹ C

(iii) Yes, there will be a transfer of mass of 12 electrons from glass rod to silk.

Transferred mass = Mass of 12 electrons

M = 12 × 9.1 × 10⁻³¹

⇒ M = 109.2 × 10⁻³¹ kg = 1.092 × 10⁻²⁹ kg

- But as this mass is very small, so it may be considered negligible.