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

One can define an alpha-volt $(\alpha-V)$ to be the energy acquired by an $\alpha$-particle when it is accelerated by a potential of $1 \,V$. For this problem,you may take a proton to be $2000$ times heavier than an electron. Then,

$A$ conductor has $14.4 \times 10^{-19} \ C$ of positive charge. The conductor has (Charge on an electron $= 1.6 \times 10^{-19} \ C$):

If a body is charged by rubbing it,its weight:

Give examples of non-conductors and conductors.

Write the law of conservation of charge. Give one example.