Question

Exercise.

Rubbing a comb on hair makes the comb get – 0.4C. 

1. Find which material has lost electron and which one gained it. 
2. Find how many electrons are transferred in this process.

Answer 1

1. The material is comb which gained electrons and the hair gained it.

2. Charge on 1 electron, e = 1.6 × 10^{– 19}C
   q = ne or n = `q/e`
   n = `0.4/1.6` × 10^{– 19} = 0.25 × 10¹⁹ = 2.5 × 10¹⁸