A polythene piece rubbed with wool is found to have a negative charge of `3 xx 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

B

Explanation

Given charge on polythene `=-3.2 times 10^-7 C`
The charge on an object is given by `q= pm n e`
The number of electrons transferred `n=(Total charge (q))/(Charge of electron ( e) ), n=(-3.2 times 10^-7)/(-1.6 times 10^-19)=2 times 10^12`
Thus, the number of electrons transferred is`2 times 10^12` . Electrons will be transferred from wool to polythene because polythene attains the negative charge that means it gains the electrons.
As the electrons are transferred from wool to polythene, the mass is also transferred because along with the charge each electron will also carry its mass.
The number of electrons transferred `=2 times 10^12`
The mass of one electron `=9.1 times 10^-31 kg`
Mass transferred from wool to polythene = Number of electrons `times` Mass of one electron
`=2 times 10^12 times 9.1 times 10^-31=1.8 times 10^-18 kg`
THus, `1.8 times 10^-18` kg mass transferred from word to polythene.
Using the concept of Gauss's theorem