Editing Fluorescent lamp (section)

====Rapid start ====
[[File:Magnetek Watt Reducer HPF Rapid Start Ballast.jpg|thumb|right|A rapid-start "iron" (magnetic) [[electrical ballast|ballast]] continually heats the [[cathode]]s at the ends of the lamps. This ballast runs two F40T12 lamps in series.]]
Because the formation of an arc requires the [[thermionic emission]] of large quantities of electrons from the cathode, ''rapid start'' ballast designs provide windings within the ballast that continuously warm the cathode filaments. Usually operating at a lower arc voltage than the instant start design; no inductive [[voltage spike]] is produced for starting, so the lamps must be mounted near a grounded (earthed) reflector to allow the glow discharge to propagate through the tube and initiate the arc discharge via [[capacitive coupling]]. In some lamps a grounded "starting aid" strip is attached to the outside of the lamp glass. This ballast type is incompatible with the European energy saver T8 fluorescent lamps because these lamps require a higher starting voltage than that of the open circuit voltage of rapid start ballasts.