• ElectricPedant (unregistered) in reply to Paulista
    Paulista:
    ... the current is half at 220v (as long as the resistance is constant).

    Correction: as long as the power is constant. W = VI

  • (cs)
    Ad Infinitum...

    Except that the story halts immediately after this header, which proves that it does not in fact go to infinity.

  • Paul (unregistered) in reply to Paulista
    As long as you use different plugs, it does make sense to have both 110V and 220V. As mentioned before, the current is half at 220v (as long as the resistance is constant). This means that thinner wire can be used to get the same power.

    Actually, if the resistance is constant, the current will be double at 220V (compared to 110V).

    I = V/R

    However, since we're talking about electronics (with voltage conversion systems to give a constant 'use' voltage) here, (not heaters) you usually have a constant power load NOT constant resistance. So, in that case, the current WILL be approximately half at 220V supply compared to 110V

    P = IV

    (If you have a transformer based voltage reduction system, then your stuff just won't work if you use a different input voltage from the one it's designed for. However Switched Mode Power Supplies (as commonly used nowadays) can be designed to work with a very wide range of input voltages, they just adjust their switching cycles accordingly - they're one of the coolest inventions ever IMHO - totally unintuitive until you're told about them, then it's so obvious)

    So, I think what you meant was right, but not what you said.

  • Zapp Brannigan (unregistered) in reply to ElectricPedant
    ElectricPedant:
    Paulista:
    ... the current is half at 220v (as long as the resistance is constant).

    Correction: as long as the power is constant. W = VI

    What was incorrect about paulista statement?

  • Paul (unregistered)

    I just can't imagine the thought process that decided that switching the voltage on a whole bank of outlets was a good idea.

    Surely it would have been a lot cheaper just to have a few spare adapters for when the executives forgot them.

    Every time the voltage was switched, users would have to switch off their PCs, crawl behind their PCs to change the red switch and then restart their PCs - the lost productivity must have been tremendous. (Not to mention all the new PSUs needed after this little incident...)

  • (cs) in reply to hikari
    hikari:
    It amuses me that this bit of standardization didn't actually require anyone to do anything. It was actually really well thought out.

    Well, I'm sure the representatives of CheapSoft, which "streamlined" their production by building their products for 220V +/- 0% only and got rid of circuit breakers cause "if it breaks, we'll be happy to sell a new one", were throwing a temper tantrum, stating how overzealous buerocracy was tieing down the economy again...

  • Anon (unregistered) in reply to Paul
    Paul:
    Every time the voltage was switched, users would have to switch off their PCs, crawl behind their PCs to change the red switch and then restart their PCs - the lost productivity must have been tremendous. (Not to mention all the new PSUs needed after this little incident...)

    More than that, presumably you'd have to announce to everybody that you are going to switch the voltage, wait for everybody to turn off their computers (hope nobody was in the middle of something important!), then switch the voltage. Then the users would still have to crawl behind their PC to flick the switch and reboot.

  • Slicerwizard (unregistered) in reply to Zapp Brannigan
    Zapp Brannigan:
    ElectricPedant:
    Paulista:
    ... the current is half at 220v (as long as the resistance is constant).

    Correction: as long as the power is constant. W = VI

    What was incorrect about paulista statement?
    Oh, nothing much. Just a direct violation of Ohm's Law.

  • (cs) in reply to frits
    frits:
    I call BS. There is this thing called a fuse in every piece of electrical equipment that plugs into a wall outlet. For those of you who don't know, they are designed to break the circuit before damage occurs from overcurrent conditions.
    Fuses are for overcurrent, not overvoltage. Surge protectors are for overvoltage, but they don't usually kick in until 330V or more.
  • (cs) in reply to Chris
    Chris:
    ... [image] These were popular in Britian in the 1920s, they allow damn near any plug to be forced into them including Europlugs, British plugs, and US NEMA plugs.
    1920s??? Really?
  • Zapp Brannigan (unregistered) in reply to Slicerwizard
    Slicerwizard:
    Zapp Brannigan:
    ElectricPedant:
    Paulista:
    ... the current is half at 220v (as long as the resistance is constant).

    Correction: as long as the power is constant. W = VI

    What was incorrect about paulista statement?
    Oh, nothing much. Just a direct violation of Ohm's Law.
    I see. I suffer from reading fail. I thought he was lowering voltage to 110 not increasing. Thnks.

  • electric knownothing (unregistered)

    (a 5 min google didn't turn up anything, maybe because i'm unfamiliar with the english terminology)

    This is something i have been wondering about, and there appear to be some people in this thread who could answer me.

    What are the (dis)advantages of 220v vs 110v. Safety maybe if you get electrocuted (though 220 is still pretty safe, i experienced myself), but are there any technical debatables to not standardise?

  • Alin (unregistered) in reply to Merus
    Merus:
    ...I read this story, and had the sudden urge to blow up a factory floor full of computers via feeding them too much electricity.

    Apparently, I should never be allowed near power boxes.

    Me too, especially if that will mean a lot less work for me in the future and I won't be held accountable for it. It's like a win win win. oh... except for those power supplies.

  • Pedantic (unregistered) in reply to Zapp Brannigan
    Zapp Brannigan:
    nB:
    that would be E=IR, not V=IR
    I don't get the nuance of E vs V. Could you explain?

    E = Electro-motive force.

  • (cs) in reply to electric knownothing
    electric knownothing:
    (a 5 min google didn't turn up anything, maybe because i'm unfamiliar with the english terminology)

    This is something i have been wondering about, and there appear to be some people in this thread who could answer me.

    What are the (dis)advantages of 220v vs 110v. Safety maybe if you get electrocuted (though 220 is still pretty safe, i experienced myself), but are there any technical debatables to not standardise?
    Do you mean standardize like the US did with the metric system? But seriously, 220v is more dangerous than 110v. You were lucky. Electricians, users and product manufacturers are more careful with 220v. Not that it would ever happen, but if the US were to convert to 220v for household current there would be many deaths, while all 3 parties were educated.
  • will (unregistered) in reply to uzytkownik

    Actually Europe has around 6 plug types in common use.

    The two round plugs, common in most of Europe, comes in 3 varieties. Some of them with work together, but you might have a problem with a plug in socket in some places.

    The british one 3 prong one.

    Switzerland, and probably Lichtenstein, use a totally different one. It has like 8 sides to the plug IIRC.

    Then italy has it own. IIRC that one has 3 prong in row, thought it was a phone jack first time I saw one.

  • anon (unregistered)

    What would happen if the set the switch on a PSU to 240V but plugged it into a 120V outlet?

  • (cs) in reply to hjd
    hjd:
    I've done this myself... and yes it is a big bang!
    That's what she said?
  • (cs) in reply to MikeDI

    I call BS on this as well. Overcurrent = overvoltage when the load is the same. Please explain to me how a desktop PSU works--all of them. because there are many different implementations to pick from, including switching supplies that can handle any number of input voltages. This is the biggest WTF yet:

    "The fuse in a standard plug (or in the wiring distribution) is NOT there to protect the device - it is there to protect the wiring TO the device."

    Typical power cord wiring will not fuse for dozens or hundreds of amps, so please tell me why you would fuse it at, say 2 amps? I have been part of a design team for electronic equipment and you can take my word that the line fuse is there to protect the device. The circuit breaker is there to protect the wiring and unrelated to the device.

  • (cs) in reply to uzytkownik
    The real probably >100 years real WTF is - who designed 2 compatible plugs with different voltages? Shouldn't they be idiotproof?

    In Europe there are 2 standards ('British' and 'continental') both running 230V.

    Or Japan, where the eastern part is on 50Hz and the western part on 60Hz!

    The only real problem I've seen is that some timers that are based on AC frequency have to have two sets of markings.

    But still, it's just ignorant.

  • (cs) in reply to frits
    frits:
    I call BS. There is this thing called a fuse in every piece of electrical equipment that plugs into a wall outlet. For those of you who don't know, they are designed to break the circuit before damage occurs from overcurrent conditions.

    Yeah I would agree with you, but I've seen it with my own eyes on my 486(100Mhz) system, when as a youngster I flicked the switch out of curiosity and forgot to flick it back. Unfortunately, my monitor was powered by the power supply and that concurrently made a loud bang with the system when I next pressed the power button.

    I wasn't too sad as it justified my self-built Pentium system with a pretty steady power suppoly.

  • Crash Magnet (unregistered) in reply to Pedantic
    Pedantic:
    Zapp Brannigan:
    nB:
    that would be E=IR, not V=IR
    I don't get the nuance of E vs V. Could you explain?

    E = Electro-motive force.

    I would think its a mater of convention. EE students learn to write their answers like:

    E = 12V

    instead of

    V = 12V

    which look kind of wierd. This also pulls in the reason EE's lean to use j for the complex operator because they use I for current. They learn to write:

    i = 12j mA

    instead of writing:

    i = 12i mA

    it just looks wierd. That an the fact that there are millions of EE's who to it one way and will kill you if you try to do it the other way. It's a standard convention.

  • (cs)

    Doing this to one computer - kind of dumb, but not a WTF. This is what I was expecting from the picture.

    Doing this to a whole room of computers - definite WTF. This is what I was expecting when I started reading the article.

    Doing this to a factory floor full of heavy equipment - EPIC WTF.

  • (cs) in reply to Crash Magnet
    Crash Magnet:
    Pedantic:
    Zapp Brannigan:
    nB:
    that would be E=IR, not V=IR
    I don't get the nuance of E vs V. Could you explain?

    E = Electro-motive force.

    I would think its a mater of convention. EE students learn to write their answers like:

    E = 12V

    instead of

    V = 12V

    which look kind of wierd. This also pulls in the reason EE's lean to use j for the complex operator because they use I for current. They learn to write:

    i = 12j mA

    instead of writing:

    i = 12i mA

    it just looks wierd. That an the fact that there are millions of EE's who to it one way and will kill you if you try to do it the other way. It's a standard convention.

    TRWTF is writing V = 12V. The only way that evaluates to true is if V equals zero.

  • ih8u (unregistered) in reply to Yazeran
    Yazeran:
    Wow!! Talk about 'going with a bang', but apart from the humor of it, quite some people could have been hurt by that blast.

    Never EVER mess with the voltage of the mains systems in a building unless you are a certified electrician for crying out loud!

    But I guess having a few spare adapters was too much for them....

    Yours Yazeran

    Plan: To go to Mars one day with a hammer

    Wow. First, I'm surprised can't find a response to you. Second, your post blows.

    Instead of having a sensible setup (like the adapters in your off-hand comment), you suggest certified electricians. Fortunately, certification means perfect and will never make a mistake -- yeah. Certification means you took a class and/or passed a test, not that you are actually all that useful in terms of the field in which you are certified.

    How many times do you hear of "certified" electricians, plumbers, contractors, etc. screwing up and screwing up royally. You know, like the kind that would make us non-certified normal jerks cringe. Get off this certified crap, fool. Never mess with ANYTHING unless you know what you are doing.

    Damn, time to switch to decaf.

  • Quirkafleeg (unregistered) in reply to Anon
    Anon:
    […] I did consider suggesting the use of [sic], but then I remembered that only arrogant douchebags would insist on pointing out everybody else's mistakes in such a passive aggressive way.
    Hello, Mr. Pot.
  • (cs) in reply to Rick
    Rick:
    But seriously, 220v is more dangerous than 110v. You were lucky. Electricians, users and product manufacturers are more careful with 220v. Not that it would ever happen, but if the US were to convert to 220v for household current there would be many deaths, while all 3 parties were educated.

    Really? I'm no electrician, but I have a friend who is, and he told me the exact opposite once. He said that 220 may hurt more than 120 because it's higher voltage, but it's actually less likely to actually kill someone because double the volts means half the amps.

    Third post attempt...

  • Your Name (unregistered)

    I am seriously baffled by how this was implemented (if the story is true as written).

    Ignoring the 50Hz/60Hz thing, did someone seriously put in a switched 2:1 step-down transformer between the distribution panel and the runs to the outlets? A transformer that can handle 20A at 120V would be pretty freaking big to be able to run safely w/o overheating for any length of time. I did a quick look through the Dale catalog to see if I could find one, but didn't.

    What makes this seem a bit incredulous is that industrial applications often times have home runs for each outlet, especially in areas where people may plug in high draw equipment. Even if that wasn't the case, the entire factory floor couldn't be running off a single circuit. Each circuit would require its own step-down transformer.

    Also, I though it was standard practice in the Europe for power runs to be loops where each end is connected to the service panel. The would really complicate sticking in a step-down transformer that you can switch in and out.

    ?

  • (cs) in reply to Your Name
    Your Name:
    Also, I though it was standard practice in the Europe for power runs to be loops where each end is connected to the service panel. The would really complicate sticking in a step-down transformer that you can switch in and out.

    ?

    Well, the article did say that their wiring was a pretty egregious code violation...

  • (cs) in reply to Mason Wheeler
    Mason Wheeler:
    Rick:
    But seriously, 220v is more dangerous than 110v. You were lucky. Electricians, users and product manufacturers are more careful with 220v. Not that it would ever happen, but if the US were to convert to 220v for household current there would be many deaths, while all 3 parties were educated.

    Really? I'm no electrician, but I have a friend who is, and he told me the exact opposite once. He said that 220 may hurt more than 120 because it's higher voltage, but it's actually less likely to actually kill someone because double the volts means half the amps.

    Third post attempt...

    Please get a third opinion before you touch wires.

    Addendum (2010-01-05 14:59):

    Mason Wheeler:
    Rick:
    But seriously, 220v is more dangerous than 110v. You were lucky. Electricians, users and product manufacturers are more careful with 220v. Not that it would ever happen, but if the US were to convert to 220v for household current there would be many deaths, while all 3 parties were educated.

    Really? I'm no electrician, but I have a friend who is, and he told me the exact opposite once. He said that 220 may hurt more than 120 because it's higher voltage, but it's actually less likely to actually kill someone because double the volts means half the amps.

    Third post attempt...

    Please get a third opinion before you touch wires.

    To be more explicit, the formula E = IR has been mentioned here a number of times. In English, Voltage is equal to Current times Resistance. If the resistance of your body remains constant, then if voltage is doubled, current will also double. Your electrician friend may not be as good a friend as you thought.

    Addendum (2010-01-05 15:08): And thank you Mason for validating my point about the need for education.

  • Jason (unregistered) in reply to Rootbeer

    Look around a Travel store.

    There are two types of power plug converters. The expensive ones have a transformer in them and down-convert from 230 to 115.

    The cheap ones simply allow you to plug into the wrong type of outlet. These are everywhere, and they're dangerous for just the reason described here.

    However, as several people have pointed out, switched transformers can frequently take a wide range of input voltages and emit a stable DC output. (These are, IIRC, also the ones you want if you're worried about vampiric power draw)

  • MS (unregistered) in reply to electric knownothing
    electric knownothing:
    What are the (dis)advantages of 220v vs 110v. Safety maybe if you get electrocuted (though 220 is still pretty safe, i experienced myself), but are there any technical debatables to not standardise?

    In the US, we use 120 V / 60 Hz because it would cost a hundred gazillion dollars to convert the whole country over to 230 V / 50 Hz.

    In Europe, they use 230 V / 50 Hz because it would cost a hundred gazillion euros to convert.

    The two are different because of arbitrary choices made long ago, before anybody thought of standardization. In fact, the US is so big that we did not have a national standard at one point -- some of our cities went through conversions from 50 Hz to 60 Hz in the early 1900's.

    Of course, this kind of thing would never affect people in the computing field -- we're all designing our systems to take into account the state of the world 100 years in the future, right? :)

    There are some minor technical tradeoffs: higher voltage * lower current carries the same power with thinner wires, but you have to make sure the rest of the system has insulation for the higher voltage, the switches withstand the bigger sparks, etc. The air conditioner in my boat can operate at 5/6ths rated capacity if you run it on 120 V / 50 Hz because the motor turns slower. But it's all just a matter of choosing an appropriate design for the system you are using.

  • Not an electrician (unregistered)

    The Real WTF is that no one has pointed out that the story says, 'his boss told him to “swap it back to 120v” just after he returned from switching it to “240v.”'

    So, if he was switching it to 120v, how'd he blow up the computers...?

  • Herby (unregistered)

    Voltages, etc... Curiouser and Curiouser... While not as exciting, there were times when my subdivision (it had underground power wiring) would get its voltage dropped from the "normal" 120 volts to a more "mood producing" voltage of around 65 volts or so (it happened a couple of times). Most of the time this did no real harm, since most things powered in a house just won't work at that low a voltage, but light bulbs had this "dim" effect, and it was December one of the times, and all the Christmas lights were dimmed, and the street lights wouldn't come on since there wasn't enough voltage for the internal arcs to start. Very moody. More fun was my TV. It used a small transformer to power the remote control circuits and that part wouldn't work, but the front panel switch would (not being a remote control) turn on the TV, as it desperately compensated for the lower voltage. Once on, the remote control circuit would work, being powered from the main source. You could almost hear the TV strain as it powered itself up. Very interesting! I do know that low voltage on such things as motors wants them (with constant loads) to draw LOTS more current and overheat in the process. If you get low voltage, be sure to turn off the furnace fan.

  • NewBee (unregistered)

    This story doesn't make sense if an American is visiting a 230V only country because it would be very expensive to make a 120V circuit just for a visitor.

    If it was someone with 230V gadgets visiting the US, it would be cheap and easy to make this crazy system happen. In the US, power is supplied from a 240V center-tap transformer. The center tap is connected to the safety ground and to the neutral bus at the fusebox. If you need a 120V circuit, you use one of the hot wires and the neutral. If you need a 240V circuit, you use both hot wires.

    All you need to make this happen is a three-way switch (Single-Pole, Double-Throw). You hook the common contact to the outlet and put one pole to neutral, one pole to the other hot wire.

  • (cs) in reply to Yazeran
    Yazeran:
    Bob:
    "...we just put in a few switches that allow electric currents..."
    "I am one of the few that cannot change current on the PC itself."

    I thought this was making fun of the "idiot" user... alas it would appear, Alex, that you confuse 'current' for 'voltage'.

    Well technically you also change the current when you switch from 120 Volt to 240 Volt Especially if you put the same resistive load on :-)

    ... and if your computer offers a resistive load, you have some other serious problems.

    For the greatest part, the regulators in the power supply will convert the input power at a near-constant efficiency to the various voltage rails for the computer. In other words, stepping up the voltage by a factor of 2 reduces the current to 1/2 it's 110 V level.

    P=IV, P is constant.

  • Forumtroll (unregistered)

    I hate to say this, but all of you who call BS (or was it schenanigans?) on this story on behalf of the circuit failsafe that was too slow, are wrong.

    You have on such circuit breakers (at least in europe) 3 different classifications in regards as to how fast they kick in. As I see it, the factory power grid had class C breakers installed where they should have had class A.

    Captcha: Esse. End of comment, esse!

  • Ron (unregistered)

    Actually these days you will find plenty of desktops without the little red switch in the back of them. These days Active PFC's are all the rage and as such most of them can automatically switch input voltages.

  • wgc (unregistered) in reply to ih8u

    IANAE (Electrician nor European) and don't know commercial code, but at least for US residential, this is a pretty blatant violation of electrical code. This is not an accident or mistake.

    It seems like something somebody's brother would do as a hack, without having any concept of electrical safety. Is there duct tape involved? If an electrician or electical inspector was involved, I hope the bribe was enough to retire on.

  • (cs) in reply to Your Name
    A transformer that can handle 20A at 120V would be pretty freaking big to be able to run safely w/o overheating for any length of time.

    There could be two separate networks, with the switches just flipping between the two.

  • systemeng (unregistered)

    Actually, lower than expected voltage can be deadly to switching power supplies. The problem is that the Field Effect Transistors (FETS) are designed with a certain duty cycle e.g. on time vs. off time. If you halve the input voltage then to first order, the transistors in the power supply stay on twice as long trying to keep the voltage stable at the regulated end of the supply. If the transistors stay on for twice as long a period, they generate twice as much heat which dissipates at the same rate at either voltage thus burning up the power supply. This is why brownouts and computers don't mix well.

  • (cs) in reply to Rick
    Rick:
    Please get a third opinion before you touch wires.

    To be more explicit, the formula E = IR has been mentioned here a number of times. In English, Voltage is equal to Current times Resistance. If the resistance of your body remains constant, then if voltage is doubled, current will also double. Your electrician friend may not be as good a friend as you thought.

    Addendum (2010-01-05 15:08): And thank you Mason for validating my point about the need for education.

    I'm thinking back to that conversation, and if I recall correctly, it might make more sense in context. We weren't talking about suddenly switching voltages like what happened here. The subject was, to deliver the same amount of electrical power, whether it would be safer to do so at 120 or 220 volts. He said that 220 was safer because it could deliver the same amount of power at a lower amperage, which is what actually determines whether or not a shock will cause real damage.

    (To put it in context, if you rub your feet on the carpet and touch a doorknob and you can feel the static spark, that's somewhere in the tens of thousands of volts, if not hundreds of thousands. But it's harmless because it's just an infinitesimal fraction of an amp.)

    Does that make any more sense?

  • rambaldi (unregistered) in reply to Mason Wheeler
    Mason Wheeler:
    Rick:
    Please get a third opinion before you touch wires.

    To be more explicit, the formula E = IR has been mentioned here a number of times. In English, Voltage is equal to Current times Resistance. If the resistance of your body remains constant, then if voltage is doubled, current will also double. Your electrician friend may not be as good a friend as you thought.

    Addendum (2010-01-05 15:08): And thank you Mason for validating my point about the need for education.

    I'm thinking back to that conversation, and if I recall correctly, it might make more sense in context. We weren't talking about suddenly switching voltages like what happened here. The subject was, to deliver the same amount of electrical power, whether it would be safer to do so at 120 or 220 volts. He said that 220 was safer because it could deliver the same amount of power at a lower amperage, which is what actually determines whether or not a shock will cause real damage.

    (To put it in context, if you rub your feet on the carpet and touch a doorknob and you can feel the static spark, that's somewhere in the tens of thousands of volts, if not hundreds of thousands. But it's harmless because it's just an infinitesimal fraction of an amp.)

    Does that make any more sense?

    ~220 is actually more dangerous but this is because most countries that work at around this point work at 50Hz. IANAD but I believe it is closer to certain frequencies in the body and thus more likely to disrupt them.

  • St Mary's Repositorium for Tired Code (unregistered) in reply to will
    will:
    Actually Europe has around 6 plug types in common use.

    The two round plugs, common in most of Europe, comes in 3 varieties. Some of them with work together, but you might have a problem with a plug in socket in some places.

    The british one 3 prong one.

    Switzerland, and probably Lichtenstein, use a totally different one. It has like 8 sides to the plug IIRC.

    Then italy has it own. IIRC that one has 3 prong in row, thought it was a phone jack first time I saw one.

    Yes, Switzerland has a different plug. See here. It is actually a room-saving one, because the plug is more compact than the German one. Funnily, the Swiss plug type is also used in Turkey, Ruanda, and partially also in El Salvador, Ethiopia, Madagascar, Maledives, Jordania and Spain. Quite a strange distribution, isn't it? In the latter country, they are called "American plugs"... :-P

  • (cs) in reply to MS
    MS:
    There are some minor technical tradeoffs: higher voltage * lower current carries the same power with thinner wires, but you have to make sure the rest of the system has insulation for the higher voltage, the switches withstand the bigger sparks, etc. The air conditioner in my boat can operate at 5/6ths rated capacity if you run it on 120 V / 50 Hz because the motor turns slower. But it's all just a matter of choosing an appropriate design for the system you are using.
    The other tradeoff that it's worth being aware of is that with lower voltage you have higher current (for the same basic power at the point of delivery). That means that you get more current in the wires, so they run hotter (the heat generated depends on the square of the current) and you've got to dissipate more of that heat or you have a fire risk.

    In short, you get to pick either a cooling problem or an electrical insulation problem; they're diametrically opposed.

  • (cs) in reply to rambaldi
    rambaldi:
    ~220 is actually more dangerous but this is because most countries that work at around this point work at 50Hz. IANAD but I believe it is closer to certain frequencies in the body and thus more likely to disrupt them.
    O RLY? [citation needed]
  • (cs)

    Um, when people forget to bring their own transformers too many times, can you fire them? :-) Solve the problem by managing it!

  • (cs) in reply to frits
    frits:
    I call BS. There is this thing called a fuse in every piece of electrical equipment that plugs into a wall outlet. For those of you who don't know, they are designed to break the circuit before damage occurs from overcurrent conditions.

    Fuse slooooooowwwwww. Overvoltagedamagereallyfast!

    This diagram shows that a 20A "fast-acting" fuse can carry 100A for up to 0.1 seconds before blowing.

    So the power supply is long dead before the fuse can react. A capacitor can blow after 1/2 cycle of current (0.008 second)...it only takes that one pulse of voltage over the capacitor's rated maximum, and it's toast.

  • Elec Tricia (unregistered)

    I recently visited the US from Europe, and all the devices I needed (cell phone charger, laptop charger, camera charger, electric shaver) already worked at 110-240V, so I only needed a plug adapter. In fact, most SMPSUs today seem to have a wide input voltage range. Those little red switches are so 1900s!

    This begs the question, were they even sure they needed to change the voltages for their overseas guests? And if they did, why not keep it at 110V if their own computers worked fine?

    Other sane choices would've included 230->110V transformers for the guests, or even a secondary wiring that's always at 110V.

  • (cs) in reply to Zapp Brannigan
    Zapp Brannigan:
    nB:
    that would be E=IR, not V=IR
    I don't get the nuance of E vs V. Could you explain?

    For resistance-current computations, EMF (electromotive force) is a more useful concept than voltage because closed-circuit voltages sum to 0 (Kirchoff's voltage law). For that use, EMF translates to "what's making the current move"...which is the "high-brow" academic interpretation.

    If you have a voltage and want to use the equation, you can substitute V for E.

Leave a comment on “The Little Red Switch”

Log In or post as a guest

Replying to comment #:

Log Out

« Return to Article