Since all elementary particles have charges which are multiples of the elementary charge on the electron, e = 1.6 ( 10 − − 19 ) coulombs, particle physicists use a different unit to express particle energies, the electron volt (eV) which makes it easier to calculate. The electronvolt is equal to the energy a particle with a charge of 1 e gains passing through a potential difference of one volt. In the above equation, if q is measured in elementary charges e and V is in volts, the particle energy E is given in eV. For example, if an alpha particle which has a charge of 2 e is accelerated through a voltage difference of one million volts (1 MV), it will have an energy of two million electron volts, abbreviated 2 MeV. The accelerating voltage on electrostatic machines is in the range 0.1 to 25 MV and the charge on particles is a few elementary charges, so the particle energy is in the low MeV range. More powerful accelerators can produce energies in the giga electron volt (GeV) range.