The electric charge on an $\alpha$-particle is ....... .

In Millikan's oil drop experiment for the determination of the charge on the electron,the reason for using oil is:

When a piece of polythene is rubbed with wool,a negative charge of $4 \times 10^{-7} \ C$ is developed on the polythene. The number of electrons transferred from wool to polythene is $\left[e = 1.6 \times 10^{-19} \ C\right]$.

How are conductors and non-conductors different? Why are they not charged by rubbing them with our hands?

How can you charge a metal sphere positively without touching it?

Can you neglect the quantization of charge?