Is it true that a light bulbs blink?

Question

My U.S. history teacher told me this last year. That we can't see light bulbs 'blink' about 30 times per sec because our eyes aren't fast enough to see that. I think that's bs, but did anyone ever heard of this?

Answer 1

I can see how someone would say that, and it might be true, to an extent.

Because lightbulbs run on AC electricity that is 60Hz (cycles 60 times per second), there are 60 times in that second where no current is flowing for an extremely small amount of time. However, lightbulbs emit light from being hot. The time that it takes the filament to cool down (and thus emit less light) is much longer than the time in which current is low or zero.

Now, there may be some undetectable amount of light loss, but even if there is, the reason you can't tell is because it's essentially undetectable, not because your eyes are not fast enough.

Also, your eyes can be fast enough to see things blinking 30 times per second. While you won't be able to count it, of course, you will probably notice that it is flickering. Many people can see a CRT computer monitor flickering when it refreshes at 60Hz.

Answer 2

In the US all Current is AC (There are of course DC adaptors). They receive current in packets like that, but they don't actually blink since it happens so fast by the time the light filiment would "turn off" and go dark it has already received more current. You can test this by taking video of a light bulb at a high shutter speed and running it back in slow motion. The bulb will never turn off.

Answer 3

Incandescent bulbs do not blink. They cannot cool down in 1/120 th of a second. (Current goes through zero twice each cycle). Fluorescent bulb do blink (60 times a second) and that's why they are always used in pairs. One fires on the positive half of the cycle, the other on the negative. You would notice it if only one worked and it would be annoying.

Answer 4

Light from a lamp using AC power blinks on and off 60 times a second. As the sine wave of the power is passing from positive to negative at 60 cycles per second, it passes through zero power for each cycle as it does so.
(In the UK it is 50 times per second).

Answer 5

Lights use alternating current. An alternating current (AC) is an electrical current whose magnitude and direction vary cyclically, as opposed to direct current, whose direction remains constant. The frequency of the electrical system varies by country; most electric power is generated at either 50 or 60 Hz (cycles per second).
The light bulb will flicker at that frequency.

Answer 6

Look for a small round silver object (relay). It is about 1 to 2 inches long, and looks like a tiny tin can. This is your signal relay switch. You could go to a parts store (Advanced Auto Parts or VW service center) and ask for it there. They should give you a diagram where it goes. The relay is an intermittent signal which makes the light blink because it's job is to cut the electricity on and off when you switch the turn signal stalk for a right (or left) turn. It is easy to replace. It just snaps in and out on two prongs, and costs about $15.00 or less.

Answer 7

Standard householf light -bulb blinks with the frequency of the supply.

In the UK this will be 50 times per second (i.e. 50 Hz)
In the US it will be 60 times per second (i.e. 60 Hz)

The human eye cannot see this amount of frames per second - your tv is approximately 25 frames per second of still images (but it fools your eyes into thinking that the pictures are moving.)

Answer 8

A.C. current in the U.S. has a frequency of 60Hz. The power in a given circuit is off for a very minute part of each second. He is correct in stating that the lights blink. Our brains are too slow to actually "see" that tiny amount of off time! ;-)=

Answer 9

Might be if the current flowing in the bulb is AC. If its DC Im sure it wont blink

Answer 10

if you ever seen current running through an object such as a lightbulb using AC, you will see that the current doesn't always stay constant. It fluctuates somtimes lower someitmes higher.

I can't remember the name of the device, but it has a screen and you can see the actuall linear represtentations of the AC current running through an object.