A question many of us repeatedly solved in high school goes like this: An electron is accellerated a certain distance by an electric field of a certain strength. Determine its final velocity. I and my teachers always treated this as a simple F=ma question, but recently it's occurred to me that a moving charge has a magnetic field, and magnetic fields store energy. Does that mean the electron would end up moving more slowly because some of the energy that goes into the electron goes into the magnetic field? Does this mean the electron has an "inertia" mass higher than its "gravity charge" mass?