"Stopping the Proton" 1. The problem statement, all variables and given/known data An infinitely long line of charge has a linear charge density of 8.00×10−12 C/m. A proton is at distance 14.0 cm from the line and is moving directly toward the line with speed 1500 m/s. I just want a better understanding of this statement: "An infinite line of charge will generate a field with only a radial component." Why, again? I can post more parts of the problem if that's too confusing.