Out of the following four dimensional quantities,which one is called a dimensional constant?

The dimensional formula for impulse is

What is the dimensional formula of an electron volt $(eV)$, and what is its value in Joules $(J)$?

Which of the following quantities has the same dimensions as that of energy?

The dimensional formula of a physical quantity represented by $\frac{e^2}{4 \pi \varepsilon_0 \hbar}$ is (where $e$ is the charge of an electron,$\varepsilon_0$ is the permittivity of free space,and $\hbar$ is the reduced Planck's constant). Note: The expression $\frac{e^2}{4 \pi \varepsilon_0 \hbar}$ is equivalent to the fine-structure constant $\alpha$ multiplied by the speed of light $c$.

If the dimensions of a physical quantity are given by $M^aL^bT^c$,then the physical quantity will be: