# CAN I 240V TO 110V LAMP

J

#### Jim

Jan 1, 1970
0
I know this may sound stupid but I have recently relocated to the
untied states from Australia I am just wondering if I bring a couple
of table Lamps that are 240volts Can I use them as they are in the
United States with 110volts or do I need to rewire them. Can you
please send any replies to me directly at [email protected]

Thankyou

Jim

J

#### John G

Jan 1, 1970
0
For lamps and other small loads the Aus wiring will be adquate but the plug
will have to be changed.
The lamp bulbs will have to be changed for 110 volt versions but if the lamp
sockets are the common (in AUS) bayonet type you may have trouble gettting
lamps to fit, most US lamps are Edison screw base.
Explore a lighting shop in your new location.
NG replies should go to NGs and not email direct so everyone can share the
replies or comment if needed.

T

#### Terry

Jan 1, 1970
0
Jim said:
I know this may sound stupid but I have recently relocated to the
untied states from Australia I am just wondering if I bring a couple
of table Lamps that are 240volts Can I use them as they are in the
United States with 110volts or do I need to rewire them. Can you
please send any replies to me directly at [email protected]

Thankyou

Jim

Jim: I was partly wondering if this was a serious enquiry!
However;
What kind of lamp (bulb) sockets do the Australian table lamps
use?
Are they bayonet type, like in the UK or are they Edison (medium
size I think?) screw in as used in North America (US and Canada).
So change the bulbs to 110 volts and change the plug to fit into
North American duplex two or three pin outlets and they should
work OK.
I presume that the wiring would be heavy enough to carry the
current required; that is a 100 watt bulb in Australia requires
approx. 0.4 amps at 240 volts. A 100 watt bulb at 120 volts
requires 0.8 amps. That's still less than one amp so the gauge of
the copper wires in the lamp plug in lead/cord would normally be
more than adequate to carry that higher current. And voltage
should be OK too since the wire is insulated for at least 240
volts.
However having said all that does the worth of a couple of table
lamps justify the amount of effort. There may be other appliances
that you will need in North America that you will have to buy.
Few if any microwave ovens for example are 'dual voltage'.
If you could plug the 240 volt lamps into 110 volts (say by
changing the plugs but leaving the lamps otherwise the same) they
would be very, very dim, giving less than one quarter the amount
of light!
Also you can buy kits of the parts that people use to make lamps
out of found objects such as big glass bottles, pieces of
driftwood etc. for a few dollars, and provided you are handy and
have a few tools convert your lamps to 120 volts using North
American bulbs and plugs, fairly easily.

T

#### Terry

Jan 1, 1970
0
John said:
NG replies should go to NGs and not email direct so everyone can share the
replies or comment if needed.

John:
I agree with your comment; I did send a copy of my comments
direct to Jim in this instance but my top posting was back here,
I have learned much from reading the questions, responses and
discussion on this and other news groups.
Often the answers alone spark other ideas and IMHO that is one of
the good things about internet news groups such as this. And
often it's "That's good info.". Or; "Why didn't think of that!".
Most technical news groups try to avoid personal criticism;
hopefully presenting opinions and information on it own merits.
What I refer to is the sort of "Well I've been in this business
for 25 years and only a moron wouldn't know ... etc. etc. etc.!"
And then, in some cases it turns into a battle of egos!
many thanks and my apologies for being a little off the topic.
Terry.

D

#### Dan Fraser

Jan 1, 1970
0
Lamps are so cheap here, they are not worth bringing with you when you
move. At a place like Fryes in LA, and at Wal Mart, who are everywhere,
you can but 6 great lamps for under $50.00. Unless it is an heirloom, don't bother. I can't even give away old lamps here because new ones are so cheap now. -- Dan Fraser From Costa Mesa in sunny California 949-631-7535 Cell 714-420-7535 Check out my electronic schematics site at: http://www.schematicsforfree.com If you are into cars check out www.roadsters.com T #### The Captain Jan 1, 1970 0 Dan Fraser said: Lamps are so cheap here, they are not worth bringing with you when you move. At a place like Fryes in LA, and at Wal Mart, who are everywhere, you can but 6 great lamps for under$50.00. Unless it is an heirloom,
don't bother. I can't even give away old lamps here because new ones are
so cheap now.

totally agree. Been there, done that, got the scars. It's going to
cost you more to ship the lamps than they're probably worth. Until
such time as we get a worldwide standard for electrical power and
appliances, its going to be a lot cheaper and simpler to buy new where
you are going.

My advice: take them to a car boot sale and get a few bucks for them.

John

J

#### John Fields

Jan 1, 1970
0
I know this may sound stupid but I have recently relocated to the
untied states from Australia I am just wondering if I bring a couple
of table Lamps that are 240volts Can I use them as they are in the
United States with 110volts or do I need to rewire them. Can you
please send any replies to me directly at [email protected]

J

#### John G

Jan 1, 1970
0
a. 6 weeks after the thread died and has disappeared from some servers and
b. When you have not got a clue what you are talking about.
Yes you can series 2 lamps to run 110 volt lamps on 240 but it is very
unwise for safety reasons and would be frowned upon by the various
authorities.
But NO connecting 2 240 volt lamps in parallel will not make them work
correctly on 110 volts. They will not com to any harm but will be very dim.
The proper thing (and fairly inexpensive.) is to change the bulbs for the
correct voltage and change the plugs for the correct type.
As they were 240 volts to start with and only lamps then the wire will be
rated for 240 volts and the double current will not be a problem.

J

#### John Fields

Jan 1, 1970
0
a. 6 weeks after the thread died and has disappeared from some servers and

---
If I don't know which servers have disappeared then someone might still
be out there waiting for a late answer. Better late than never say
never I always say.
---
b. When you have not got a clue what you are talking about.

---
Oh really? Well I'll have you know that the only reason I suggested
that he wire them in parallel is because it's very hard to shorten the
filament. Not only that, changing the lamp socket is a job best left to
a qualified electrician type not to mention the plug.
---
Yes you can series 2 lamps to run 110 volt lamps on 240 but it is very
unwise for safety reasons and would be frowned upon by the various
authorities.

---
Hahaha you're wrong trying to run two 110 volt lamps in series is only
220 volts and connecting them to 240 volts would only leave 20 volts
unaccounted for, not very dangerous because of the amps. From home's
law, since the difference in voltage is 20 volts and the resistance of
the two in parallel is 1/2 of what it would be normally, 20
volts/(1/2)ohms = 40 amps, which is very low impudence.
---

J

#### John G

Jan 1, 1970
0
John Fields said:
and

---
If I don't know which servers have disappeared then someone might still
be out there waiting for a late answer. Better late than never say
never I always say.
---

---
Oh really? Well I'll have you know that the only reason I suggested
that he wire them in parallel is because it's very hard to shorten the
filament. Not only that, changing the lamp socket is a job best left to
a qualified electrician type not to mention the plug.
I never suggested changeing the socket but if the Untied states do not have
bayonet plug lamps then that's their loss.
I did not say the OP should change the plugs himself but many people are
capable of doing it .
110, 220, 240, most people see this as within the range of supply variations
and would not argue about it in the case of lamps.
From home's
law, since the difference in voltage is 20 volts and the resistance of
the two in parallel is 1/2 of what it would be normally, 20
volts/(1/2)ohms = 40 amps, which is very low impudence.

No , the total resistance is half what it would be with only one lamp and so
the total current will be twice that of one lamp. Absolutely nothing to do
with volts/(1/2)ohms = 40 amps or 4.4kilowatts.

F

#### Fred Abse

Jan 1, 1970
0
I don't think he saw the smiley, John.

J

#### John Fortier

Jan 1, 1970
0
If you wire two 240 volt lamps in parallel, the voltage applied across each
is still 110 volts. So each lamp will glow, but dimly.

P=E^2/R, so the power generated in each lamp, which in an incandescent lamp
is used to cause the filament to glow, will be, relative to the power
generated when connected to 240 volts, 110^2/240^2 or 12100/57600 which is
approx 0.21. So your two lamps connected in parallel to 110 volts will
develop 42% of the power of one lamp connected to 240 volts.

John

J

#### John Fields

Jan 1, 1970
0
If you wire two 240 volt lamps in parallel, the voltage applied across each
is still 110 volts. So each lamp will glow, but dimly.

P=E^2/R, so the power generated in each lamp, which in an incandescent lamp
is used to cause the filament to glow, will be, relative to the power
generated when connected to 240 volts, 110^2/240^2 or 12100/57600 which is
approx 0.21. So your two lamps connected in parallel to 110 volts will
develop 42% of the power of one lamp connected to 240 volts.

---
Well, John, I'm afraid you've missed a couple of things, the first being
the tongue-in-cheek smiley at the end of my post and the second being
the effect of the temperature coefficient of resistance of tungsten on
the power dissipation of the lamp with a 110VRMS input.

Just for grins, I hooked up a couple of 120V 100W lamps in series and
ran them using a 240VRMS 60Hz source. I measured the current through
them and got 0.81A. 240V*0.81A = 194.4W, pretty close to what it
should be.

Then I reduced the voltage to 110V and got 0.53A, so the lamps were
dissipating a total of 58.3W.

Bottom line? A 240V incandescent lamp with 110V across it will
dissipate 58.3W/194W ~ 30% of what it would with 240V across it, so two
240V lamps in parallel connected to 110V mains will dissipate about 60%
(not 42%) of what a single 240V 200W lamp will when connected to 240V
mains.

If you care to pursue the matter further, here's a pretty good link:

http://www.phys.uu.nl/~vndijk/thesis/node142.html

T

#### The Captain

Jan 1, 1970
0
John Fields said:
---
Well, John, I'm afraid you've missed a couple of things, the first being
the tongue-in-cheek smiley at the end of my post and the second being
the effect of the temperature coefficient of resistance of tungsten on
the power dissipation of the lamp with a 110VRMS input.

Just for grins, I hooked up a couple of 120V 100W lamps in series and
ran them using a 240VRMS 60Hz source. I measured the current through
them and got 0.81A. 240V*0.81A = 194.4W, pretty close to what it
should be.

Then I reduced the voltage to 110V and got 0.53A, so the lamps were
dissipating a total of 58.3W.

Bottom line? A 240V incandescent lamp with 110V across it will
dissipate 58.3W/194W ~ 30% of what it would with 240V across it, so two
240V lamps in parallel connected to 110V mains will dissipate about 60%
(not 42%) of what a single 240V 200W lamp will when connected to 240V
mains.

If you care to pursue the matter further, here's a pretty good link:

John

http://www.phys.uu.nl/~vndijk/thesis/node142.html
deals with the temperature co-efficient of hot wires in a convective
atmosphere.

"you will have to wire your 240V lamps in parallel to get them to work
here. ;^)" With or without "smiley" this is misleading.

And I think John, that with or without the details of resistance
change with tremperature, you, yourself, have proved the silliness of
connecting the lamps in parallel.

Actually, Jim, the simplest and most pragmatic solution, which I have
had to use myslef, is to change the lamp fittings. They aren't
permanent installations, since manufacturers know they may get bent or
broken. So a quick trip to your local hardware store for screw in
sockets and bulbs and the necessary American style plugs is really the
simplest, easiest solution.

I have one lamp which has had a 220 volt screw in socket in Germany
(where I bought it) a 240 volt bayonette socket in England and now a
further 110 volt screw in socket in the States. It hasn't exploded
yet!

John

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