Positive charge in an atom is:

The increasing order for the values of $e/m$ $(\text{charge/mass})$ is :

Which of the following particles cannot be accelerated by an electric or magnetic field?

The mass of the proton is $1840$ times that of an electron. If a proton is accelerated through a potential difference of $1 \,kV$,the kinetic energy of the proton would be

The number of electrons in the nucleus of $^{12}C$ is

The nucleus of an atom can be assumed to be spherical. The radius of the nucleus of mass number $A$ is given by $1.25 \times 10^{-13} \times A^{1/3} \ cm$. The radius of the atom is $1 \ \mathring{A}$. If the mass number is $64$,then the fraction of the atomic volume that is occupied by the nucleus is: