if electricity is sinusoidal then why bulb do not blink?

Answer 1

I sort of agree with the others, but not quite.

It does go through zero volts twice a cycle (120 times a second), but the bulb warms up and glows.

It is near zero so little of the time that it never cools down enough to really "blink off". There would be some oscillation, but it would be heavily filtered by the slow thermal cycle.

Answer 2

the bulb does blink. The problem is that you're not wired to be able to see it. Actually that's not a problem. I'd guess it's a blessing. Many people get headaches if they have to work in fluorescent-lit rooms, because the cycling is more obvious. Also the color rendition is poorer (though it is improving).

Next gen lighting will be rooms lit by LEDs and fiber optics. Right now fixtures are very expensive and are mostly for high end projects. But cost of operation is much much less expensive, since with LEDs and fiber the light is not a biproduct of a heating device, (where the heat is often an undesireable side effect that then must be compensated for with air conditioning, etc.)

Answer 3

Most of the answers given are actually wrong.
1. Our eyes CAN detect a 60 Hz light signal, however, the filament (the metal strip that produces the light) in a lightbulb has something called latency. Due to the latency the light bulb is never fully on or off. Therefor we only see it as on.

You could clearly see a 60 Hz signal passed to a low-latent LED.

Secondly: Electricity IS NOT sinusoidal, AC Electricy is. whereas DC electricity is not.

Answer 4

I like most of the other answers.
Especially the bit about the bulb being too hot to cool as the power goes through it's cycle. In Australia we used to have our trains run on 25Hz (meaning 50times a second for the power sinusoid) the dimming could be seen on these. With fluorecents (some have mentioned these) some people are anoyed by the flicker i suggest getting the electronic high frequency version.

Answer 5

It does.... except your eyes can't see it, and the regular light bulb can not react fast enough.

The regular AC is 120V but the peak is actually at 120 * sqrt(2) which is 170 volts. It reaches this peak 120 times a second, and it crosses ZERO volts 120 times a second. (60Hz) The light bulb is basically a heat element that happens to generate light also. Because it has a heat mass, the reaction time is too slow to actually follow this change.

If you have a fluorescent bulbs, they do blink. If you don't believe me, look directly at the fluorescent bulbs, and swing an object (like pencil) very fast between your eyes and the bulb. You'll notice, you see a strobe motion. That's the proof it is switching on and off 120 times a second.

Answer 6

Almost all electrical power in the United States is generated with a sinusoidal voltage that oscillates from the peak voltage of +170 volts to - 170 volts and back to + 170 volts at the rate of 60 times each second. The effective voltage important for power condiderations is then 120 volt (rms or root-mean-square voltage). The resulting AC current also has a sinusoidal variation with time, i.e. the electrons change the direction of flow 120 times each second. (In other countries, rms voltage of 240 volts and frequency of 50 Hz is used.) But again, no matter in what direction the electric current happens to flow, at any instant of time the number of electrons entering a device is equal to the number of electrons exiting that device.

Answer 7

The frequency is too high for the eye to see. Some areas in New York City used to use 25 Hz current, and you could see flicker in light bulbs used on such power.

Answer 8

Once the filiment reaches incandesence (white hot) it simply doesn't have time to cool off at 120 zero volt cycles per second. Unless we specifically design a method to "freeze" the cycles (strobe), we don't perceive of a flouresent light flicker because of persistance - i.e. our eyeball's mechanics simply can't turn off and on that quickly - that's why TV's and movies don't flicker when we watch them.

Answer 9

the frequency is so high, that we do not see the bulb pratically blinking.

Answer 10

it blinks but human eyes cannot sense this blinking