Lighting
Lamps, tubes, LED drivers, ballasts — making light
Incandescent / Halogen Lamp
Lamp
A tungsten filament heated white-hot by current — the original electric light. Beautiful colour rendering and dimming, terrible efficiency (~95% of the power leaves as heat). Halogen versions run hotter and last longer via the halogen recycling cycle.
LED Bulb / Tube / Panel
Lamp
An array of white LEDs plus a built-in driver in a retrofit shape — the lamp that ended a century of filaments. 100+ lm/W, 15,000–25,000 h life, instant start, and now the default light source for everything.
Fluorescent Tube / CFL
Discharge Lamp
A mercury-vapour arc generates UV that a phosphor coating converts to visible light — 4–6× more efficient than incandescent. The straight 'tubelight' with its choke and starter ran India's homes and offices for decades; the CFL folded the same tube around a screw cap.
HID Lamp (Sodium / Metal Halide / Mercury)
Discharge Lamp
High-intensity discharge lamps make light from an arc in a high-pressure gas — the orange sodium glow of older Indian streetlights and the white floods of stadiums. Being replaced by LED, but still everywhere and still in every EE syllabus.
Ballast (Choke) & Starter
Lamp Control Gear
Discharge lamps have negative resistance — once struck, they'd draw runaway current without a ballast to limit it. The magnetic choke + glow starter pair is the classic tubelight circuit; electronic ballasts replaced both with a high-frequency inverter.
LED Driver
Power Supply
LEDs need controlled current, not just voltage — the driver converts mains to a regulated constant current (or constant voltage for strips), sets the brightness, and largely decides how long the light lives.