Electric Charges And Fields

Question

A polythene piece rubbed with wool is found to have a negative charge of 3.2 x 10^–7C.
a) Estimate the number of electrons transferred (from which to which?)
b) Is there a transfer of mass from wool to polythene?

Solution

Given, Charge - q = - 3.2 \times 10^{7} C and charge on electron - e = - 1.6 \times 10^{- 19} C ∴ number of electrons transferred q = ne n = \frac{q}{e} = \frac{- 3.2 \times 10^{- 7}}{- 1.6 \times 10^{- 19}} = 2 \times 10^{12}

b)
Electrons are transferred from wool to polythene during rubbing as polythene has negative charge.

Mass of an electron, m =

9.1 \times 10^{- 31} kg

No. of charge, n =

2 \times 10^{12}

Therefore, amount of mass transferred= = 2 x 10¹² x 9.1 x 10^–31 kg = 18.2 x 10^–19 kg.