Leonardo Da Vinci

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Q. about Mortal Kombat

A. look at this section: Mortal Kombat#Development it'll explain why it has a "K" instead of a "C". Why they chose that name, well is their own opinion. Sincerely Subzerosmokerain (talk) 00:05, 30 May 2010 (UTC)

Ohm's law

I have removed the following post of yours from Talk:Ohm's law. It is not appropiate for an article talk page: such pages are meant for discussing improvements to the article, not discussion of the subject itself - see the talk page guidelines. You may, however, like to post your question at the Wikipedia Science Reference Desk, where the volunteers will be delighted to provide answers. Also please note that new posts go to the bottom of the page on Wikipedia, not to the top. Thanks, SpinningSpark 16:13, 26 March 2011 (UTC)

The law is not applied always

I recently had a problem with an ungrounded power socket(there wasn't a ground wire at all). And what I discovered is in the chasis of my computer there was a phase of 110 volts AC! Even the phase meter lighted. My point is Ohm's Law doesn't apply in my situation and I ask why? The current passing at the computer chassis was very small. Something like maybe 5-10 mA - enough to hit me like it did but not a serious damage at all. So my problem is why there is such a high voltage but so small current? I know my body has like 100 kiloohms but this is not the case. Maybe because it is generated by a computer power box(impulsive generator). But then again why this current/voltage would be detected with my multimeter and my phasemeter if it is high frequency? Also why the current is so small but not like some amperes as for Ohm's law given the low resistance of the computer chassis :).--Leonardo Da Vinci (talk) 15:04, 26 March 2011 (UTC)

The reason is that the 110 volts was being sourced through a high impedance path. Ohm's law works just fine - you just don't know about everything that's in the path. Just because the computer case itself is of low resistance, does not mean that the voltage did not come through a high-Z path before it got to the case. And just because you measure 110 volts with a multimeter does not mean it's 110 volts from a direct connection to phase. It is actually very common in ungrounded equipment to find such "leakage" voltage on the chassis, especially when measured with a DMM, which typically has have an input impedance of 10 megohms - it doesn't take a lot of current from the source. Your phase test lamp uses a neon lamp, which similarly needs very little current; those small neons will often light if you connect one end to phase and just hold the other, with no obvious connection from you to ground or neutral.

Where does the voltage come from? In a device with a linear power supply (not a PC) it's often due to leakage in the insulation of power transformer windings. A lot of ungrounded audio gear will have a pair of very small "grounding capacitors" that deliberately connect both sides of the AC line to chassis; since the chassis is also the "return" for the audio signals this provides an RF ground that works well enough to allow the chassis to act as an RF shield for the high gain audio paths. In the case (no pun intended) of a PC it is probably leakage through a varistor and/or capacitor in the PSU, these being connected betweeen the "hot" AC input prong and the chassis (probably from "neutral" to chassis also to allow for miswired sockets, which as you know, are common). Jeh (talk) 18:05, 26 March 2011 (UTC)

Thanks a lot. But if the voltage is passing though a lot of resistance shouldn't it be a lot lower? --Leonardo Da Vinci (talk) 18:16, 26 March 2011 (UTC)

Not when you're measuring it with a very high impedance meter, hence not drawing appreciable current. Voltage drop through a resistor is proportional to the current - that's Ohm's Law for you. Or to put it another way, with resistances in series, the Vdrop through each R is proportional to that R's contribution to the total R.

I don't know where you got the "10 mA" figure but let's say that's correct. Then assuming 120V at the source that is an effective R of 120V/.01A = 12K ohms. Now measure the voltage with the 10 Mohm meter. We now have the Vsource in series with two Rs, total R in the circuit is 10012000 ohms. The voltage drop across the mysterious resistance is then 12000/10012000 of the total Vdrop in the circuit. Since the total Vdrop in the circuit is 120V, the drop across the R is 120 x 12000/10012000 = 0.14 volts. The meter on the other hand will drop 120 x 10000000 / 10012000 = 119.96 volts, and that's what it will read. That's why we build meters with such high-impedance inputs. If we didn't they could draw appreciable current from the DUT and so give false readings.

For another example - if you put DC voltmeter probes on your car's battery positive and at the starter's "battery" terminal, you will normally measure zero volts. But if you do this while starting the car you'll see a volt or two while the starter turns the engine. Reason, it's drawing a lot of current (usually well over 100 amps) and even though the cable is very large, that causes voltage drop in the cable's (very slight) resistance. Jeh (talk) 07:13, 27 March 2011 (UTC)

The problem in capacitors - lot of PC power supplies have capacitors conected between hot wire and chasis and between neutral wire and chasis. As air resistance between PC chasis and nearest grounded metal parts is too high, voltage drop is low and phasemeter shows some lethal voltage. Sometimes people feel spasms touching ungrounded PC chasis, sometimes not. If the person is physically good healthed, this shock won't be serious or lethal. But some persons with weak health may get electric trauma and even heart fibrilation, which is not good. By the way, what prevents you to buy grounding wire and line it from ungrounded power sockets to main panel? It will be more faster, safer and angrier, than assume if anyone can get shock or not. As I see, you have old house, which have been built while conception "electrical safety" were flying somewhere in the sky and your existing electric installation is very far from modern wiring codes 90.191.190.76 (talk) 18:44, 29 March 2011 (UTC)

I don't get the part " As air resistance between PC chasis and nearest grounded metal parts is too high, voltage drop is low" Jah the person before your reply seems to point it is mathematical and the resistance is very high in the ohmmeter so it measures higher voltage to compensate for the low supply of current and the high resistance at the chasis(maybe?). Well the power socket is far away from the main panel and it would be hard and almost pointless. Now with short circuited ground to neutral wire I have no problems :). 0 volts at chassis. The power socket is in the wall how will the wire pass through the other wire's way to the panel without damaging the whole house? This thing is made while building the building :D. --Leonardo Da Vinci (talk) 09:47, 30 March 2011 (UTC)

It is very danger to use neutral as the ground. Line ground wire separately, even on the wall surface. Someone may drill hole in the wall and casually drill your neutral - PC chasis will have lethal voltage on it. Please install everything correctly. For second, circuit must be closed to carry current, if you touch only hot wire, nothing wrong will happen - circuit should be closed to neutral to carry some current. 90.191.190.76 (talk) 15:05, 30 March 2011 (UTC)

But still hot wires can hit you AC or DC. They have requirements like closed cirtuit or being grounded via the touching body somehow. Can small current hit me enough to be released via air with high humidity? Once I've just taken a shower and I was hit by 220 volts(not sure phase or neutral wire) but the only effect was my left hand was hurting and being stoned for like 10 seconds maybe. Nothing too serious although I was the whole wet and barefoot.--Leonardo Da Vinci (talk) 20:01, 31 March 2011 (UTC)

I am still confused. (hot and neutral wires have same resistance because of the equal length of the cables let's say 10 ohm's for each wire) but we have a consumption circuit like a house(let's say 10 ohm's again) and 100 applied voltage the amperes are 10A in the hot wire, 1A in the housing and 0.1A on the returning wire. 3x10 ohms in serial. It equals 30ohms. 3,33A must be the sending and returning currents on both wires :D. But the consumator must be something directly working at AC.--Leonardo Da Vinci (talk) 07:10, 1 April 2011 (UTC)

I'm afraid you are confused to the point where a Q and A here is not going to help much. First, 10 ohms would be very high for each wire in house wiring - the total R from breaker panel to outlet should be a fraction of an ohm, even counting all of the splices (wire nuts) and screw connections. Second, you do count the hot and neutral wires in the total R in the circuit, but not the ground wire, as significant current does not usually flow through it. Third, if 10 A are flowing in the hot wire then 10 A are coming back through neutral - or in neutral and ground together, but again, the current in ground is supposed to be insignificant. The electrons don't get "used up" or even stored anywhere. Jeh (talk) 08:10, 1 April 2011 (UTC)

I kinda don't understand the "smart" electrons behavior. I have the feeling They already know even before the current start to flow how much resistance (the current will encounter) there will be in every single segment/sector of a given random circuit. It's not like you always give max current and it drops at the consumption circuit but because of the resistance it will encounter the current will be pre-lowered because it is "smart" :). I am currently reading "Lessons in electric circuits Volume I DC" - great book!--Leonardo Da Vinci (talk) 09:25, 1 April 2011 (UTC)

• 1) Even if wire resistance is 10Ω (5Ω hot wire and 5Ω neutral wire), they don't consumpt energy, cause circuit is not closed. When you plug table lamp to receptacle, light bulb shorts hot wire to neutral and current begin to flow in closed circuit. This way you calculate:

a) R(final) = R(transformer) + 2R(wires) + R(light bulb)

b) I = U(transformer) / R(final) and result will be in Amperes

If you short hot to neutral, you consider only R(final) = R(transformer) + 2R(wires) without R(light bulb), it is named "short-circuit-current". If value of short-circuit-current wouldn't be enough to beat out circuit breaker, you'll have fire cause of overheated wiring.

If hot wire is not shorted to neutral or ground, current will flow to nowhere and consumpt 0 watts. Cause cable insulation and receptacle insulation between hot and neutral is ~2 000 000Ω, so if you calculate 110V / 2 000 000Ω = 0.000055A and 110V x 0.000055A = 0.00605W, which can't feel your electricity meter, so 0.00605W is approximately 0 watts. Clear?

• 2) As for safety position, >48V are danger for human, so 48 volts and more can kill someone. Probably you have more good health and 220V can't break you. But oficially, all appliences since 48 volts are danger and should have ground or dielectric cover. Bathrooms should have safe extra low voltage, usually it is 12V; so it is nothing to do for 220V in bathroom or shower.
• 3) DC is direct current and AC is alternate current. Your retail company gives you AC (cause it's cheaper), but some appliences (like TV-set) have diodes to rectify current from AC to DC.
• 4) Electrons...

• a) Let's begin from DC - imagine water in pipe. So you take your flashlight - electrons begin to flow from battery "+" to battery "-" through light bulb if circuit is closed. Understand? If the circuit is open, current will flow to nowhere and light bulb won't shine. Clear?
• b) Then go from DC to your retail company - nobody will install batteries or accumulators to each building. They use more cheap way - alternators on power plant, where "+" and "-" change place several times per second due to alternator's spining. But in simplifying purposes, electricians say, that current goes from hot wire to neutral (like in DC, but this statement is not correct). 90.191.190.76 (talk) 19:49, 2 April 2011 (UTC)

Speaking of DC the electrons move from - (negative) to + (positive) electrode of the battery :). Because more free charged electrons are located at the negative side of a given circuit/source and so they start to move to the positive given the force of attraction like in the P-N junction. Also there really is 220 Volts in my bathroom I measured them. ;D They are used primaly for powering a fan to clean the air after taking a shower. Given what I read today in another book it is better to be wet if you get hit by a lightning and maybe the current passed too easy via my wet skin and grounded to earth via my bare feet thus not inflicting serious damage to my organs. But I read 0.1-0.2A is more deadly current than higher curret (maybe 5-10 amperes) because this little current is preventing the heart from working normally while bigger current will cause more severe damage to tissues/organs. It's kinda get like a paradox. --Leonardo Da Vinci (talk) 21:38, 2 April 2011 (UTC)

• 1) Yes, cause - is marked as + and + is marked as -.
• 2) Probably bathroom fan is installed in wrong place if you can touch it. Also, 220V appliences are forbidden near water, wet rooms should contain at least IP44 appliences.
• 3) For first, you need to know resistance of your body. If your body resistance is 1000Ω and you apply 220V to it, you'll get 220/1000 = 0.22A. If your body has resistance 1500Ω, you'll get 0.14A by 220V shock. That is why you should use RCD/GFCI in bathroom circuits. But if your health is good, you're running every morning, you push-up, sit-up, lift barbell and etc every day and live without eating in fast-food - your body will recovery faster after electric shock and even organs won't be damaged. 90.191.190.76 (talk) 08:25, 3 April 2011 (UTC)

90.etc. is maisktan on several counts.

Electrons flow from - to +, period, end of discussion. The terminal marked as + is +, and the one marked as - is -. It is not actually the case that there are more electrons at the - terminal of the power supply than at the positive (unless your PS is a capacitor) - the EMF just works in that direction, pulling electrons into the positive terminal of the supply and pushing them out the negative.

Way back in Ben Franklin's time, a wrong guess was made as to the polarity of the charges that flow in wires, and Franklin and others declared "electricity flows from positive to negative." Today we know that electrons are negative and that they flow from the negative terminal of a power supply, through a circuit, and back into the positive terminal. However the old idea is still (believe it or not) prevalent. It is (if writers are being careful) referred to as "classical current flow" and we still think in these terms for certain types of design work. Examples: The "right hand rule", in which the thumb points in the direction of "current", uses classical current flow, positive of the supply to negative of the supply - if you want to use the actual electron flow you have to use your left hand. In a circuit with a single DC supply that is positive with respect to ground (like nearly all logic design), we commonly think in terms of "current" or "power" flowing from the positive supply rail, through the devices, to ground. The arrows in the diode and transistor symbols point in that direction, and a "current sinking driver" (very common in many kinds of "interface" chips) is one that apparently provides a path for this "classical current flow" to ground. Yet all the time, the electrons are flowing in the opposite direction, from ground to the positive supply rail. There are even design areas where we work with both models at the same time.

Rules about voltages in bathrooms vary from country to country. But I travel a lot (35 countries so far) and I have yet to see a hotel bathroom that didn't have a 120V or 220V outlet - in most places outside North America, they tend to have both. But per almost all modern codes these must be guarded from delivering dangerous shocks in some way: Either by a "residual current device", aka "ground fault circuit interrupter", which will open the circuit if there is any appreciable imbalance between the current in hot and neutral; or else the outlet is supplied through a transformer that provides ground isolation. The transformer also makes it impossible to use high current devices like hair dryers there. Bathroom outlets in N.A. do not have a transformer, but they are required to have the RCD/GFCI. To protect you in older buildings, hair dryers have had the RCD/GFCI built into their power cords for the last 20 years, at least. Either the transformer or the RCD/GFCI keeps you from getting a dangerous shock if you provide a path between hot and earth ground (like a wet path to the drain pipe, assuming the drain pipe is metallic). The transformer though would not save you if you provided a path between its two terminals. (I have never ever EVER seen a 12 volt outlet in a bathroom, nor any credible allusions to the existence of such anywhere in the world. What would you plug into it?)

Good exercise habits and good health do not much protect you from most of the dangers of electric shock. The primary danger is of fibrillation, and it doesn't matter how strong the heart muscle is when a few tens of mA of AC flow through them - the normal neural impulses are completely swamped no matter how strong the heart is. Nor does recovery from fibrillation after the shock ends get any easier with a stronger heart, as that is all a feedback loop in the nerves. Similarly for diaphragm paralysis, another common way to die from electric shock: Having a stronger muscle doesn't mean you have any more ability to overcome the paralyzing effect of the current. Please see http://www.faqs.org/docs/electric/DC/DC_3.html for more on electrical hazards and safety procedures.

Regarding the "smart" electron behavior... they don't have to know in advance of meeting the resistance later in the circuit. Rather there are already electrons in all parts of the circuit, long before a supply is connected. Remember that the electrons coming out of the negative terminal of your battery, or coming out of the neutral of your wall outlet during a positive-going half-cycle in the AC, are not the same ones that will be returned, at least not for a while (never, in the case of AC). Rather there are free electrons all through the entire circuit path. When electrons leave your supply they have to push on the ones in the immediately adjacent supply wire. Those push on the next ones, etc. Some of them enocunter more resistance, some less, and the overall resistance is "felt" by the ones leaving your supply. The speed at which this is "felt" back at the supply is the speed of signal travel in the circuit, usually around 0.7C for non-reactive wiring and loads. If you use the "water pipe analogy" (which has a lot of problems, but never mind), remember that the "pipes" all are filled with water long before being connected to the pump (the battery).

The velocity of the actual electrons though is very low; it's literally a slow walk! Look up "electron drift velocity." Jeh (talk) 14:11, 4 April 2011 (UTC)

For first, let's see statistics about electric chair - some people die there being shocked less than 1 minute, some people die only after 2 or even 3 minutes. And voltage there is always 3000V. So, person with stronger heart will recover more faster after electric shock; but for persons with weak or ill heart even 110V might be lethal. Why only few people die after direct contact with mains AC, but much of people still alive?

For second, better to say "current flow" instead of confusing in "+ to - or - to +". And perfect comparing is water flow in the pipe (if we're talking about DC).

For third, wiring rules are similiar, they differ only little from each other. In Russia and Europe neutral should be grounded in main box one more time and divided into working neutral and protecting neutral - the same in America. Little differences in voltage, construction of fuse box and panel products, but it is nothing. What is really big mistake in America - it is saying, that split-phase system is two-phase system. In fact it is single-phase system taken from 3-phase system with tap in the middle of transormer.

As for bathroom, mains AC is allowed nowhere near water. It might be allowed only far from water, where you can't touch 110V applience by your hand while taking bath or shower. And 12V is used for lamps near bath or shower (near water), 12V sockets are missing there. Transformers were used lot of time ago (even in old USSR buildings you can find 20W transformer in bathroom, which converted 220V to 220V), but nowadays they are not used. 90.191.190.76 (talk) 19:47, 4 April 2011 (UTC)

1) Yes, some people survive longer in the electric chair than others. But your conclusion that this is primarily due to their physical condition is pure speculation on your part. As for AC line shocks, the primary variability is in the path of the current. If it doesn't go through your heart or your diaphragm muscles, it isn't likely to kill you quickly.

2) It is not always "better to say current flow." If you mean classical current flow, the mythical flow from + to -, fine. If you mean actual electron flow, - to +, you say "electron flow." Perhaps the usage is different in other languages but that is most certainly the convention in English, and this is English language Wikipedia.

The water pipe analogy breaks down very quickly even for DC. It is useful only for a grade-school-level explanation and has been responsible for altogether too many misunderstandings. Even for DC. Once you have said "EMF is somewhat like the pressure applied by a water pump," and "a higher resistance wire is somewhat like a smaller diameter pipe," you should throw it away. There's no such thing as turbulent vs. laminar electron flow, for one thing. And while both electricity and water will follow multiple parallel paths of different resistance, electron flow is divided (re. Ohm's law) in inverse proportion to the resistance of the paths, but water's behavior is decidedly non-linear.

3) The split-phase system IS two phases to an electronics engineer. Put the two two hots, relative to neutral, on a scope and try to tell me they are not 180 degrees out of phase with each other. However in electrical wiring practice we actually don't call it a two-phase system (to avoid confusion with places that are supplied with two out of the three usual phases). Instead the two hots are referred to as "legs."

4) Sorry but you're flatly wrong; there is no rule that 120 "isn't allowed near water." Every house, apartment, and hotel room I've ever been in in the US has 120V straight from the hot "leg" in the bathrooms and kitchen. In recent practice such do have to be protected by an RCD/GFCI, but I assure you, there is no rule that says you can't have a 120V outlet in a bathroom or kitchen, or near the utility sink in the garage. Want another example? How about my friends' apartment in Paris? There's a 240 outlet in the bathroom, or else the "charging" LED on my shaver was lying. Similarly, there are 240 outlets in their kitchen for various appliances, quite obviously not current-limited.

As for transformers, a very, very, very large percentage of hotel bathrooms worldwide (as I said, I travel a lot), including brand new construction, do have them. (Very commonly the brand name is "Voltage Valet".) The hotel I was just in in London had them, and it's been recently renovated. So do the bathrooms in the BA lounges at Heathrow T5, very recently built. "Nowadays they are not used"? Sorry but yes they are. I've seen them. Don't tell me I haven't. Jeh (talk) 04:25, 5 April 2011 (UTC)

Electrocution and some other questions

Which current is easier to hit a man at the same voltage? I remember once getting hit by around 10 AC volts and I measured them with a Multimer. I usually read that you require 36 volts DC to get hit. DC seems a lot more powerful than AC if we speak about equal voltage and the current is continuous and there isn't skin effect. Is it easier to perform electrocution in the meaning of executing/killing a man with DC electric current? Also how is current given to earth via dust in the electric board?--Leonardo Da Vinci (talk) 20:08, 25 March 2011 (UTC)

I have removed the above post from Electric current talk page. Please do not start discussions about the subject on article talk pages which are meant for discussing improvements to the articles. A better place to ask knowledge questions is WP:RD/S. Also, new threads go to the bottom of the page on Wikipedia. Thanks, SpinningSpark 18:26, 3 June 2011 (UTC)

what's inside the light bulb?

"There is a wolfram wire which glows while big current pass through it. The bigger the current the brighter the glowing ;). Electrons are rubbing and generating heat/glowing by side effects of the rubbing"..... incorrect the answer is the chemical element 'Sodium'urName (talk) 14:39, 24 January 2015 (UTC)