What would use up more power a light constantly on or it flashing off and on?

Answer 1

good question! i member my mum would say not to flash the lights on and off cause it waste elec.

Answer 2

Although the frequency (and mark/space - the off-on ratio) make a difference, the general answer would be constantly on uses more power.

It is true that for an incandesent lamp, extra power DOES flow for a split second - this is why bulbs often "pop" when you first switch them on, a cold filament will draw many times as much current as a white hot one. However it is white hot in a TINY fraction of a second - at which point power consumption becomes constant (assuming voltage remains constant)

As for burning out faster, it is true that it is most stressed at the time it is switched on BUT tests have shown than a bulb will still give nearly its full rated life when being flashed - but when it DOES finally go, it will usually be when it is being turned on.

A car indicator bulb is a good example of something flashed a good deal - or the beacon at the nearest crossing - these lamps are not overly special - and DO last for an incredibly long time.

As for fluro tubes, yes, for a short time (a few seconds perhaps) then considerably more current flows than normal - but the old nonsense of leaving them on all the time because they use less power than one turned on only when it is needed, is a nonsense - urban myth stuff. Some lamps DO however become more efficient when the phosphors have warmed up - so although consumption does not decrease, optical ouput INcreases.

With regard to the guy talking about the meter wheel, I am skeptical that the few milliseconds of extra flow could be truly observed by anyone - and quite possibly wouldn't even be enough over that duration to overcome the inertia of the wheel in question! I stand corrected if he was referring to a 3KW theatre flood :)

Answer 3

The lamp is only drawing power when it is on - so flashing it 50% on 50% off will only draw half the power (on average) of the same lamp left on 100% of the time.

This is used to reduce the power consumed by some LEDs which are pulsed at rates too high for the eye to detect and reduce the overall power consumption. You can see the effect by moving your eyes quickly over the light which will then appear to be a string of dots rather than continuous streak.

There are a couple of HOWEVERs.
1) Incandescent lamps, as some folks have pointed out, will burn out quickly when flashed in this way - this is because a cold filament has a realtively low resistance and so when current is allowed to flow, there is a very high 'inrush' current that can cause local heating beyond the steady state capacity of the filament and melt it. This inrush current also represents a large power drain although only for milliseconds.
2) Flourescent lamps also require a high initial power surge to strike the arc across the tube and during this time the power factor is not balanced - this can be significant enough to warrant leaving flourescent lamps permanently on rather than turning them off for a few minutes when you leave the office.

Answer 4

Assuming an incandescent light, constantly on will use more power. A light is not like an electrical motor, which requires more power to start up because more power is required to set a stationary object in motion than to maintain a moving object at it's current velocity (physics 101). It is strictly a function of the material the filament is made of, which emits photons (and heat) as a reaction to the energy absorbed while the electrons move through it.
A florescent light,and most other plasma/gas lights (like mercury vapor) however, do use a little extra power on start-up, because a capacitor (think of a "battery" that can discharge all its energy at once) needs needs to be charged so that it can spark and "excite" the gas in the tube that emits the light.

Answer 5

It depends on a lot of variable's, however it is safe to say that a blinking light would use more power than a equal llight that is steady on. A steady light is nothing more than a switch a bulb and a power source while as a blinking light must have a relay at the very least which is going to use power. However the difference when talking about small automotive type bulbs is going to be very very minimul you would mostlikely not even be able to tell.

Answer 6

A light constantly on. Flashing it on and off cuts and restores power.

Answer 7

A light that is constantly on in a car will use more electricity and run your battery down faster than a light that flashes on and off.

Answer 8

Well, if it's a regular light bulb (incadescent) then the bulb staying constantly "on" would use more power.

If, it is a florescent bulb then the bulb flashing would use more power (use is in powering up to full brightness).

You leave a lot for assumptions here, you are talking about 120 volt light bulbs and electrical power aren't you?

Here's a simple electrical power formula for you....

Power (watts) = I (amps) x E (volts) or P=IE or PIE.

Thank Me.

Answer 9

It's the oldest wives tale since Edison invented the bulb. The surge when a light comes on lasts for about a tenth of a second. Any electrician who tells you that leaving the lights on is cheaper is a first class idiot.

Answer 10

Its definitly flashing the light on and off

Answer 11

Depends on the frequency of the flashing. If it was two to three years between flashes???