Why atoms are electrical neutral ? 

What is shown by Thomson's experiments of electric discharge through gases ? And explain the plum pudding model.

The ratio between total acceleration of the electron in singly ionized helium atom and hydrogen atom (both in ground state) is

What is impact parameter ? 

Which one of the relation is correct between time period and number of orbits while an electron is revolving in a orbit

Assertion: The specific charge of positive rays is not constant.
Reason: The mass of ions varies with speed.