What is the charge on an electron?

When a piece of polythene is rubbed with wool,a charge of $-2 \times 10^{-7} \ C$ is developed on the polythene. What is the amount of mass transferred to the polythene?

When a proton is accelerated with $1 \, V$ potential difference,then its kinetic energy is .......... $eV$.

Which experiment was used to determine the quantization of electric charge?

Assertion $(A)$: Electromagnetic force is enormously strong as compared to gravitational force. Yet,gravity dominates in large-scale phenomena (e.g.,formation of galaxies).
Reason $(R)$: Existence of positive and negative charges makes matter mostly electrically neutral.
Which of the following is true?

The sure check for the presence of an electric charge is