Ballasts & Circuits
 All fluorescent lamps must have a supplementary component, commonly known as a ballast, to limit the current and to provide the necessary starting voltages. Each ballast is specifically designed for its operating service voltage and other characteristics.
2-lamp ballasts are either lead-lag or series-sequence design. In the lead-lag variety, each lamp operates on its own independent circuit one leads and the other lags. This provides a high power factor (between 90 and 100%) and practically eliminates all stroboscopic effects. 
In the popular series-sequence design, the lamps start in sequence and when fully lighted operate in series. These ballasts also operate at high power factor but don't correct for stroboscopic effect.
And Furthermore . . .
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