Problem: How can American 110V light bulbs be used on a 240V grid?

In summary: I have several times connected 240 V bulbs to 110 V outlets. They do not burn out immediately, but they do not last long. I do not see any problem connecting two 110 V lightbulbs to the 240 V outlet. What would happen if you turned on the switch?I think that the question is about the voltage of the bulbs, but it is not clear from the conversation. ehildI do not think there is any problem with the voltage supplied to the bulb. The voltage of the bulb is equal to the voltage of the source. The voltage across the bulb in the 110 V outlet is 110 V and the voltage across the bulb in the 240 V
  • #1
pstir2
19
0

Homework Statement


In America power is supplied at 110 V. In Australia power is supplied at 240 V, however American lights are routinely used in Australia.
a) How is this possible?
b) Calculate the power that a pair of 1000 W 110 V light would dissipate when plugged into a 240 V system in series.
c) Calculate the power that a 1000 W 110 V light would be required to dissipate when plugged directly into a 240 V system.

Homework Equations


V=IR
P=VI
P=(V^2)/R
P=(I^2)V
Total Resistance = R1 + R2 + R3 + ... + Rn

The Attempt at a Solution



I'm not sure if this is correct or even going in the right direction.

A) I'm not sure. I am not great at the conceptual side of this subject.

B)
Resistance of one bulb
P=(V^2)/R
1000=(110^2)/R
R=12.1

Total Resistance = R1 + R2
=12.1+12.1
=24.2

Power from outlet
P=(V^2)/R
P=(240^2)/24.2
P=2380.17W

Power Dissipated = 2380.17-2000
=380.17W

The two lightbulbs in series would need to dissipate 380.17 Watts of power.

C)
P=VI
1000=110I
I=9.09A

P=VI
P=240x9.09
P=2181.81W

Dissipated Power = 2181.81-1000
= 1181.81W

The lightbulb would need to dissipate 1181.81 Watts of power.

Alternate Answer to 'C'

Resistance of one bulb
P=(V^2)/R
1000=(110^2)/R
R=12.1

Power from outlet
P=(V^2)/R
P=(240^2)/12.1
P=4760.33W

Power Dissipated = 4760.33-1000
=3760.33W

The lightbulb would need to dissipate 3760.33 Watts of power.
 
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  • #2
What were your answers to a and b? How did you arrive at those?
 
  • #3
Those voltage values are RMS values I believe. Usually they are controlled by a series of transformers along long power grids.
 
  • #4
pstir2 said:
b) Calculate the power that a pair of 1000 W 110 V light would dissipate when plugged into a 240 V system in series.
c) Calculate the power that a 1000 W 110 V light would be required to dissipate when plugged directly into a 240 V system.

B)
Resistance of one bulb
P=(V^2)/R
1000=(110^2)/R
R=12.1

Total Resistance = R1 + R2
=12.1+12.1
=24.2

Power from outlet
P=(V^2)/R
P=(240^2)/24.2
P=2380.17W

Power Dissipated = 2380.17-2000
=380.17W

The two lightbulbs in series would need to dissipate 380.17 Watts of power.

The power dissipated on a lightbulb is the whole electric power. It transforms to heat and light. The two bulbs in series dissipate 2181 W. A single bulb dissipates half of it, 1090 W which does not exceed the nominal value too much. The bulbs will not burn out. You can use two 110 V bulbs connected in series to the 240 V system.


pstir2 said:
C)
P=VI
1000=110I
I=9.09A

P=VI
P=240x9.09
P=2181.81W

This is wrong. The current is not constant, it is proportional to the voltage across the lightbulb. It is the resistance that can be taken constant.

pstir2 said:
Alternate Answer to 'C'

Resistance of one bulb
P=(V^2)/R
1000=(110^2)/R
R=12.1

Power from outlet
P=(V^2)/R
P=(240^2)/12.1
P=4760.33W

Power Dissipated = 4760.33-1000
=3760.33W

The lightbulb would need to dissipate 3760.33 Watts of power.
Again, P=V2/R is the dissipated power. Do not subtract the nominal value.

Plugging in a single bulb to the 240 V outlet would make the bulb burn out as the power is more than four times the nominal value.

ehild
 
  • #5
American lights are routinely used in Australia.
Incredible. A cite please.
 
  • #6
I do not think that anybody really tries to connect two bulbs in series. But the lamps are usually equipped with a transformer and they can be used with both 110 V and 240 V bulbs.

ehild
 
  • #7
ehild said:
the lamps are usually equipped with a transformer and they can be used with both 110 V and 240 V bulbs.
Which type/s of lamps and bulbs would this be?
 
  • #8
I only guessed... I have seen such switch for 110/230 V supply voltage on other devices.

ehild
 
  • #9
1. Homework Statement
In America power is supplied at 110 V. In Australia power is supplied at 240 V, however American lights are routinely used in Australia.
a) How is this possible.
Hi pstir2. I'd be interested to learn where you got this question from. Can you give further details?
 
  • #10
ehild said:
The power dissipated on a lightbulb is the whole electric power. It transforms to heat and light. The two bulbs in series dissipate 2181 W. A single bulb dissipates half of it, 1090 W which does not exceed the nominal value too much. The bulbs will not burn out. You can use two 110 V bulbs connected in series to the 240 V system.




This is wrong. The current is not constant, it is proportional to the voltage across the lightbulb. It is the resistance that can be taken constant.


Again, P=V2/R is the dissipated power. Do not subtract the nominal value.

Plugging in a single bulb to the 240 V outlet would make the bulb burn out as the power is more than four times the nominal value.

ehild

For "A" where did you get 2181W from. Can you show all calculations like I have.
 
  • #11
pstir2 said:
For "A" where did you get 2181W from. Can you show all calculations like I have.

I copied your incorrect one. I meant 2380 W.
 
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  • #12
NascentOxygen said:
Hi pstir2. I'd be interested to learn where you got this question from. Can you give further details?

That's all the information that I have. This isn't a practical question for my house, car, etc. Its a question to go on a yr 11 Physics exam that I'm writing.
 
  • #13
pstir2 said:
That's all the information that I have. This isn't a practical question for my house, car, etc. Its a question to go on a yr 11 Physics exam that I'm writing.
I see. It's just a made-up scenario. :eek:

Anyway, the highlighted part is not correct. Perhaps you might think of some way to rework it so as to not mislead.
In America power is supplied at 110 V. In Australia power is supplied at 240 V, however American lights are routinely used in Australia.
a) How is this possible?

As for a plausible response to (a), I have been stumped for an answer and waiting eagerly to see the expected answer here. The only answer I can come up with is that the American manufacturer produces a version with a 240V filament for the Australian market. I can't conceive of anyone routinely operating a series pair of 110V incandescents off 240V.

Perhaps you were contemplating more of a theoretical short-term emergency measure? That would be the go!
 
  • #14
As an Australian this is news to me! We use bayonet & edison plugs.

I woud presume if we are talking about a single inancdescent light bulb, the filament may support 110V, 240V or more. The brightness would vary with voltage.
 
  • #15
As I understood, incandescent lamp bulbs are banned in Australia. The other kinds of bulbs are expensive, and look ugly. So it is worth buying old-type bulbs somewhere else.

I saw an URL where it was explained how to use two US bulbs connected in series, but I could not open it, and can not find it any more. It needs some design, but it can be solved and I think, there might be people in Australia who did it, and sell such lamps, chandeliers...

ehild
 
  • #16
ehild said:
As I understood, incandescent lamp bulbs are banned in Australia.
Nope. Though I know some people believe that.

Incandescent bulbs are available in every supermarket! Even if none was available, people would import the right voltage bulbs from China, or Brazil, or wherever, certainly not mess around with 110V bulbs on the country's 240/250V supply.

I think the "emergency" proviso would endow a suitable ambience for this question on a test paper, though, as the idea does make people think.

Wait on ... perhaps the examiner was thinking of that other Australia? The one with no kangaroos...you know, where they filmed The Sound of Music?? :wink: Maybe incandescents are banned there?
 
  • #17
Incandescent lamps are banned in the EU above power of 60 or 40 W. http://en.wikipedia.org/wiki/Phase-out_of_incandescent_light_bulbs It was done gradually, first the 100 W bulbs were withdrawn and then the 75 W ones. Even the 40 W and 25 W bulbs are rare and there are no frosted bulbs. You can still buy halogen lamps but they are much more expensive then the ordinary bulbs were, and they are sensitive of switching on and of. You can buy compact fluorescent light bulbs and LED-s. The first ones look ugly, their light is not good to the eye and if burnt out, you can not throw them into the litter bin, as they contain mercury. The LEDs are better, but still look ugly and they are very expensive.
I have my last frosted candle bulbs in my chandelier and if one of the eight burns off, I have to buy a new chandelier.

I do not know what you mean on the other Australia, as I know the Sound of Music was filmed in Austria. It belongs to the EU, and the old type incandescent lamps are banned there just like in my country, Hungary.

ehild
 
  • #18
Just to enter the incandescent ban discussion, I think it is a good thing even if the LED lights look a bit worse. The main objective of a lamp should be to provide light and the incandescent light bulb is very inefficient at doing so. In fact, a German retailer tried to circumvent the ban by selling the incandescent bulbs as "miniature heating elements". With regards to price, the LED lights have a significantly longer life-time which more than makes up for the price difference in terms of better price/usage time. I admit that the first time I bought LED lights I was under the same impression, but it is essentially a one-time investment while you regularly have to replace incandescent bulbs.

For heating, there are more efficient ways of doing it than using the electricity directly. In my house, I am using a air-to-water heat pump. Living in Sweden, this has cut my utility bill in more than half. (You can imagine the electricity cost in Sweden in winter ...)
 
  • #19
I like the idea of "miniature heating element".
I think that cheap and well-working things should not be banned. If there are better lighting elements, people will buy them, but deprive them from the old ones is quite cruel. The new ones cost about 100 times more... Also the factories in Hungary which produced incandescent bulbs (very good ones, working quite many years, and not polluting the environment) had to be closed down.

Halogen lamps are available still . They are hot, get burnt quite soon, and all of them are clear, bad to the eyes.
I just do not understand the whole thing.

As for heating with some more efficient way, there are lot of people who can not manage it. Living in a small flat in an apartment house you do not have too many possibilities. Gas or electricity here.

ehild
 
  • #20
I don't draw a distinction between the old incandescents and the double-bulb halogens, they both rely on an incandescent filament. It's the latter that are available in supermarkets, along with the lower power novelty incandescents. I, too, would have expected halogens to be intolerant of ON-OFF cycles, but car headlight halogens seem to live on and on, so I'm not so sure. The old cheap incandescents had been showing shorter and shorter lives before they were phased out, I assumed this was because high quality bulbs had been elbowed out of the market by the cheap-and-nasty Chinese import.
 
  • #21
Even if the LED lights cost a 100 times more, they have a lifetime which is a about 25 times longer (and you get the extra comfort of not having to exchange them as much) so just from lifetime you get back a significant chunk of the initial investment. An LED light has a lifetime ranging in the order of 25000 hours.

An incandescent 60W bulb gives around 750 lm. The power of a LED light producing a similar light is around 10W. Over the lifetime of the LED light, this amounts to a saving of 50x25000 = 1250000 Wh = 1250 kWh.
Assuming you pay order 10 euro cents per kWh (this is a low price, at least in Sweden), you would save 125 euros over the lifetime of the light. This should be more than enough to offset the price of the light itself, even if you could get incandescent bulbs for free, LED lights in Sweden do not cost more than order 10 euro at most.

With regards to pollution, with the current distribution of power production, drawing more energy results in pollution even if the bulb itself does not.
 
  • #22
We replaced 15 x 50W Halogen downlights in our kitchen with 15 x 5W LED bulbs from ebay. The LEDs use a 1/10 of the electricity and are brighter. The beam angle is also wider so we get fewer shadows. We opted for warm white LEDs and the colour is similar but I admit not exactly the same. You very quickly get used to the slight difference. Been so impressed that we are replacing as many other bulbs with LEDs as possible.

If you are considering LEDs make sure you understand what a Lumen is and think about the effect the beam angle has on apparent brightness. (As a guide I usually look for downlight bulbs producing >400 Lumens). I'm sure lots of people end up disappointed because the LEDs they buy have a wider beam angle than the downlight bulb they had previously. Indeed the ones we have look dimmer if you compare one LED to one Halogen BUT when used in a grid the beams from the LED overlap and the overall brightness is actually higher. LEDs aren't always perfect drop in replacements for incandescent but if you know what you are doing they can be better.
 
  • #23
ehild said:
As I understood, incandescent lamp bulbs are banned in Australia. The other kinds of bulbs are expensive, and look ugly. So it is worth buying old-type bulbs somewhere else.

High efficiency ones are readily available. And funnily enough they are at a higher price than the old ones that were phased out.
 
  • #24
NascentOxygen said:
The old cheap incandescents had been showing shorter and shorter lives before they were phased out, I assumed this was because high quality bulbs had been elbowed out of the market by the cheap-and-nasty Chinese import.

Here, in Hungary, the incandescent bulbs were the product of Tungsram, a very old an famous factory with its own Research Institute. http://en.wikipedia.org/wiki/Tungsram . Now it is owned mainly by GE (General Electric). The bulbs were good, lasted for 4-5 years. I never saw Chinese bulbs here. I used to work in that Research Institute of Tungsram...

ehild
 
  • #25
ehild said:
Here, in Hungary, the incandescent bulbs were the product of Tungsram, a very old an famous factory with its own Research Institute. http://en.wikipedia.org/wiki/Tungsram . Now it is owned mainly by GE (General Electric). The bulbs were good, lasted for 4-5 years. I never saw Chinese bulbs here. I used to work in that Research Institute of Tungsram...

ehild

I am sorry if the ban has affected you personally. However, this does not change my preference between incandescent bulbs and LED lights as I believe the LEDs are cheaper in the long run and provide light at a higher efficiency.
 
  • #26
NascentOxygen said:
Wait on ... perhaps the examiner was thinking of that other Australia? The one with no kangaroos...you know, where they filmed The Sound of Music?? :wink: Maybe incandescents are banned there?

:rofl:
 

1. How can American 110V light bulbs be used on a 240V grid?

There are two main options for using American 110V light bulbs on a 240V grid. The first is to use a step-down transformer, which will convert the 240V electricity to 110V, allowing the light bulbs to function properly. The second option is to use a voltage converter, which will also convert the 240V electricity to 110V, but may be more expensive and less efficient than a transformer.

2. What is a step-down transformer?

A step-down transformer is a device that lowers the voltage of an electrical circuit. It works by using two sets of coils, one with more turns than the other, to step down the voltage. This allows 240V electricity to be converted to 110V, making it safe for American 110V light bulbs to be used on a 240V grid.

3. What is a voltage converter?

A voltage converter is a device that converts the voltage of an electrical circuit. It works by using electronic components to change the voltage of the electricity passing through it. This allows 240V electricity to be converted to 110V, making it safe for American 110V light bulbs to be used on a 240V grid. However, voltage converters may be more expensive and less efficient than step-down transformers.

4. Can I use a power adapter to use American 110V light bulbs on a 240V grid?

No, a power adapter alone is not sufficient for using American 110V light bulbs on a 240V grid. Power adapters are designed for use with electronic devices, not high-voltage appliances like light bulbs. Using a power adapter without a step-down transformer or voltage converter can result in damage to both the light bulbs and the grid.

5. Are there any safety concerns with using American 110V light bulbs on a 240V grid?

Yes, there are safety concerns to consider when using American 110V light bulbs on a 240V grid. Without the proper equipment, such as a step-down transformer or voltage converter, the light bulbs may overheat and potentially cause a fire. It is important to follow proper safety precautions and use the appropriate equipment when using American 110V light bulbs on a 240V grid.

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