Nothing stays lit without voltage, every electric circuit has a time constant that determines how fast it discharges once the voltage source is removed. That is a factor of the inductance, resistance, and capacitance. You can be a weenie and calculate it if you know all of those factors, Its staying for a short time because the circuit has some sort of overall capacitance for its power factor that stores the charge. Thats what they do. -j/wc
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