A proton moves 2.00 cm parallel to a uniform electric field of E = 200 N/C. (a) How much work is done on the proton by the field? (b)What change occurs in the potential energy of the proton? (c) What potential difference did the proton move through? I really just need help with Part A, I should be able to get through the rest alright. I'm not entirely sure what the charge of the proton would be. I know that wok is equal to the change in potential energy, which is then equal to (kq1q2)/r.....but I'm not sure what the chrages would be. Help?