The proton and neutron are collectively called as

The charge on a positron is equal to the charge on which one of the following?

Identify the correct increasing order of $e/m$ ratio for the following particles: $n, p, e, \alpha$.

The ratio of specific charge of a proton and an $\alpha$-particle is

Fill in the blanks:
$(i)$ $R. A. Millikan$ developed the ......... method to determine the charge of an electron.
$(ii)$ The positively charged particles in a modified cathode ray tube are called ............ .
$(iii)$ The smallest and lightest positive ion obtained from hydrogen is ........... .
$(iv)$ In the year $1932$,$Chadwick$ discovered ........... .

The increasing order (lowest first) for the values of $e/m$ (charge/mass) for: