Why Don't ac Bulbs Flicker?

Though we have ac supply in our homes, all the bulbs seem to glow with constant brightness. why is it so?
- ABHISHEK ROY (age 18)
BHILAI,CHATTISGARH,INDIA

In India., ac current is at 50 Hz. So there are 100 current pulses per second, counting back and forth as two pulses. Each pulse heats the filament. The time between the pulses is too short for the filament to cool down much, so the glow is almost constant. Your eyes/brain can't consciously distinguish flickers faster than about 30 per second, so even if there were a little flickering at 100 times per second, you wouldn't see it consciously.

Some fluorescent bulbs directly use the ac current, rather than using electronics to convert it to higher frequencies. Their light stops more quickly when the current isn't flowing. These bulbs do flicker at 100 times per second (120 in the U.S.). Again, that's hard to see directly although there are reports of subconscious effects. They can be used, however, with stroboscopes to clearly see the effects of the flicker.

Mike W.

(published on 01/01/2014)