Question

A glass rod rubbed with silk acquires a charge of +8 × 10⁻¹² C. The number of electrons it has gained or lost
(a) 5 × 10⁻⁷ (gained)
(b) 5 × 10⁷ (lost)
(c) 2 × 10⁻⁸ (lost)
(d) –8 × 10⁻¹² (lost)

Answer 1

Correct option ⇒ (b) 5 × 10⁷ (lost )


Given in the question :-

Charge = 8 × 10⁻¹²
Charge on an electron, e = 1.6 × 10⁻¹⁹

Applying the formula , we get

n × e = 8 × 10⁻¹²
n = 8 × 10⁻¹² / 1.6 × 10⁻¹⁹
n = 5 × 10⁷ .

Hence the number of electron it lost is  5 × 10⁷ .
So glass rod acquires positive charge , hence it is clear that it lost 5 × 10⁷ electrons.


Hope it Helps :-)

Answer 2

Answer:

q = n × e

n = q/e

n = 8×10^-12 / 1.6×10^-19

n = 5×10^7 electrons.

(b) 5× 10^7 ( gained).