Question

which physical quantity does electron volt measure ? How it is related to si unit of quantity?

Answer 1

Electron volt (eV) is used to measure energy or threshold energy or work function, The SI unit of energy is joule (J).

Electron volt or eV is the unit of energy (electrical energy).
e V = 1.6 * 10⁻¹⁹ coulombs (charge of an electron) * 1 volt
= work done to bring an electron from infinity to its current location
having a potential of 1 Volt.

Potential energy of a system of charged particles =
= charge on one particle * potential voltage at the location of that charge due to the presence of other charges.
= work done to bring the charge from infinity to that location in presence of other charges