Light is a form of electromagnetic radiation. Lamps can be broadly classifies as follows:
ELECTRIC ARC LAMPS
GAS DISCHARGE LAMPS
An important characteristic of any discharge is that, once started, the current tends to increase instantaneously to a destructive value. A choke (referred to as ballast) is incorporated in the AC circuit to limit the current to a safe value.
Fluorescent and Discharge Lamps have a inherent low power factor of the order of 0.4 lag to 0.5 lag. Power factor is improved by the use of capacitor having capacitance value ranging from 3 MFD to 45 MFD and power factor is corrected to 0.85 lag to 0.90 lag which is acceptable for proper utilization of power. The capacitor provides a low impedance path to interference currents & helps to by pass any third harmonic currents.