The work W done by the electric field in moving the proton is equal to the difference in electric potential energy of the proton between its initial location and its final location, therefore:
where q is the charge of the proton,
, with 
being the elementary charge, and 
and 
are the initial and final voltage.
Substituting, we get (in electronvolts):
and in Joule:
where q is the charge of the proton,
Substituting, we get (in electronvolts):
and in Joule: