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Author Topic: Car battery, Transformer, Inductance Charger, Mains Power, etc.  (Read 2556 times)
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Hello!
I have lots of questions:
1) I've heard the a car battery can generate 12V @ 500A (6000W [or am I wrong?])! If I try to power my Arduino with this power (not that I'm gonna), or simply touch the terminals with my hands, will I get hurt?
2) That means that you can use a transformer to step up the power to 110V @ 54A from a car battery?
3) What is the amperage of mains power in Canada?
4) Why does the green box transformer in the neighborhood vibrate and hum?
5) What is inductance? Is it electromagnetism, or "inducing" a current in another coil using EM?
6) How does an inductance charger induce a current in a toothbrush if there is no return path for electrons?
7) Will this cause the same amount of damage to a human: 110V @ 15A, 500V @ 3.3A, 1650V @ 1A, 82500V @ 0.02A (they are all 1650W [V * A])?
smiley-cool Should this be posted under bar sport or general discussion?
9) If mains power's ground (reference point) is the Earth, and reference points are usually the negative terminal, would electrons be drawn out of the Earth (a current is draw out of the - terminal of the battery, and returns to the + terminal)?
10) If static shocks are 10000V+, does static electricity have an amperage or wattage?
11) What's you're opinion on this: http://amasci.com/emotor/nostat.html ?
12) Does the Earth have to be a good conductor to be a reference point for electricity?

Fact: "Currents are often regarded as flowing from + to -; a legacy of ancient misunderstandings." - quote from a book.
Thanks!
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Hello!
I have lots of questions:
1) I've heard the a car battery can generate 12V @ 500A (6000W [or am I wrong?])! If I try to power my Arduino with this power (not that I'm gonna), or simply touch the terminals with my hands, will I get hurt?

A car battery will only supply such peak currents for a few seconds before the voltage will sag. And no you will not be shocked from a 12vdc source voltage. However if you were to say short circuit a car battery across a metal wristwatch band you were wearing is could turn near incandescent and burn you severely.

2) That means that you can use a transformer to step up the power to 110V @ 54A from a car battery?

No, a transformer can pass only AC voltages not DC voltages. And as said a car battery will not supply 500 amps for more then a few seconds.

3) What is the amperage of mains power in Canada?

It's limited in the size of the main and distribution circuit breakers installed in your home service box. Here in US most are limited to 200amps total and most circuit branches are limited by 15, 20, or 30 amp branch circuit breakers.

4) Why does the green box transformer in the neighborhood vibrate and hum?
Not sure what kind of transformer you are describing, but AC power runs at either 50 or 60 hz in most countries and that can be heard if it causes the transformer winding to mechanical vibrate in the transformer metal core.

5) What is inductance? Is it electromagnetism, or "inducing" a current in another coil using EM?
Current flowing in a wire cause a magnetic field to be developed, or imposing a changing magnetic field to a wire will cause a changing current to flow in the wire. Best to study basic AC theory to get a better understanding of induction and capacitance.

6) How does an inductance charger induce a current in a toothbrush if there is no return path for electrons?
It's basically just a transformer AC coupled power circuit and there is no requirement for a DC return path as the transformer secondary winding inside the toothbrush allows a current to flow because of the magnetic field  coupling the primary and secondary windings.

7) Will this cause the same amount of damage to a human: 110V @ 15A, 500V @ 3.3A, 1650V @ 1A, 82500V @ 0.02A (they are all 1650W [V * A])?

The higher the voltage the higher the shock risk to personal. The amount of current to flow through a human is dependent on the resistance of the path through the human and obeys Ohm's law as to how much current will flow. Current is not 'forced' it is 'drawn' by a load resistance following ohms law. Because a voltage source has a maximum capacity of say 15amps does not mean every load will draw 15 amps. Study ohms law to understand the relationship of voltage, current, and resistance.
smiley-cool Should this be posted under bar sport or general discussion?
Doesn't matter to me, I just scan 'all new posts' and rarely even read what subsection it's posted in. But then again I'm not a moderator that is tasked to care about such things.  smiley-wink
9) If mains power's ground (reference point) is the Earth, and reference points are usually the negative terminal, would electrons be drawn out of the Earth (a current is draw out of the - terminal of the battery, and returns to the + terminal)?
No. First, mains power does not have negative and positive terminals as it's AC not DC voltage. Only DC voltage sources have fixed positive and negative terminals. Earth ground is often used as a common point to wire all ground wires together at one central point in AC power systems, however there is no current flowing into or out of the earth. Grounding can be a very complex subject and easy to misunderstand. But there is no requirement for a true 'earth ground' for current flow in circuits.

10) If static shocks are 10000V+, does static electricity have an amperage or wattage?
Yes if there is a current path for the voltage to flow, but the voltage alone does not provide enough information to calculate the amount of current flowing in such a case. Joules is a more common metric used in characterizing static short term voltage discharges rather then wattage. Again current can only flow in a complete circuit and the amount of current is depended of the resistance of the circuit path. Voltage alone does not provide enough information to analyze circuit performance. Ohm's law dictates the relationship between voltage, current, and resistance. You must know two of the terms to calculate the third term.
 
11) What's you're opinion on this: http://amasci.com/emotor/nostat.html ?
Not really very educational, seems more rather a 'rant' about terms used. Static electrical properties are well understood by industry, so I don't really get the authors point or concerns.

12) Does the Earth have to be a good conductor to be a reference point for electricity?
No. A battery powered radio does not require a earth ground, so for electronics circuits to function do not depend of earth. Earth grounding is usually only important for allowing a high current path for lighting protection. Don't confuse circuit common connections with earth grounding connections. They are sometimes the same physical connection as in house AC power input wiring, but having the circuit common wired to a grounding rod is not a requirement for circuit operation but rather as a safety requirement.

Fact: "Currents are often regarded as flowing from + to -; a legacy of ancient misunderstandings." - quote from a book.

That is a ancient argument of what direction electricity flows in a DC circuit. Electricity theory predated the knowledge of the basic atom structure, so they didn't even understand about electrons being the current carrier in a conductor even though they knew that something was flowing. So they stated and agreed that current flowed from positive to negative. Today we know that electrons flow from atom to atom from negative to positive charged atoms. So ever sense we have to live with the awkward statement that current and electrons flow is in opposite directions. They even came up with the concept of 'hole flow' to try and fix the discordant. It doesn't matter in the big picture but electron flow (negative to positive) is the more accurate explanation in my opinion.

Thanks!
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Grounding is a confusing topic: http://arduino.cc/forum/index.php/topic,104134.0.html
I still don't really get why if you touch a bare high voltage wire while standing on the floor, why do you get hurt? Where's the return path for electrons? Another grounding issue!
Quote
Current is not 'forced' it is 'drawn' by a load resistance following ohms law.
What happens when a load draws more current than the source can provide (e.g. short circuits, 3V @ 380mA motor)?
Quote
No, a transformer can pass only AC voltages not DC voltages.
Well, if you invert the power to AC, then you probably can!
Thanks for answering my questions! smiley
« Last Edit: May 11, 2012, 03:08:53 pm by dkl65 » Logged


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Grounding is a confusing topic: http://arduino.cc/forum/index.php/topic,104134.0.html
I still don't really get why if you touch a bare high voltage wire while standing on the floor, why do you get hurt? Where's the return path for electrons? Another grounding issue!
Yes, if you feel a shock then there is enough current flow to cause it. There are few 'perfect insulators' if the applied voltage is high enough. Even air is not a perfect insulator or else there would be no such thing as lightning bolts.

Quote
Current is not 'forced' it is 'drawn' by a load resistance following ohms law.
What happens when a load draws more current than the source can provide (e.g. short circuits, 3V @ 380mA motor)?

Every real voltage source has some internal resistance value that will limit the maximum short circuit current that can flow even into (and especially) a 'perfect' short circuit. So ohm's law still governs the situation.

Thanks for answering my questions! smiley
« Last Edit: May 11, 2012, 12:14:54 pm by retrolefty » Logged

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Yes, it's impossible for a substance to have no resistance at all. I still don't get why if you stand on the Earth and touch to high voltage wire, you get hurt. That means that electricity surges through you! I'm not so concerned about resistance here. Where's the return path (or is there)? A current can't flow through one path with no return. If you don't stand on the Earth (like birds), you won't get hurt. That means that it has something to do with the Earth (grounding again!) Static electricity has no return path, because it jumps randomly, but what about current electricity from the bare wire?
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dkl65
I still don't get why if you stand on the Earth and touch to high voltage wire, you get hurt. That means that electricity surges through you! I'm not so concerned about resistance here. Where's the return path (or is there)?
Basically the high voltage wire is starting in a electricity power plant. The electricity power plant is "grounded" which means it is attached to the ground. In other words the sine wave neutral is kind of like (not sure how exactly but it is) connected to the ground.
If you are standing on the ground any AC voltage from a electrical power plant will have a potential difference between you and the wire.
And yes the ground is an insulator but not the water that is available in the ground.
And there is your loop. ground -> powerplant -> powerline -> you -> ground (you have been fried  smiley-mr-green)
Note that when hanging on a power line you will not be fried. (just like the birds sitting on those wires are not) If the fire brigade comes with a ladder that touches you; you are fried  smiley-mr-green .

Best regards
Jantje

PS pure H20 is not conductive but normal water is.
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And yes the ground is an insulator but not the water that is available in the ground.
So that means that I am connected to power plant via the water in the Earth? Sorry, grounding+insulation still has me confused (there is enough water in the Earth to conduct to the power plant?). Also, why does my iPod charger release some sound that sounds like a cross between clicking and humming all the time when plugged in, and emits a high EMF measured by my Arduino EMF Detector, compared to other transformers (chargers)? Why are some plugs for appliances "polarized" (one lead bigger than the other) when AC is supposed to have no defined terminals? Is the word "lead" (as in leads (terminals) of a battery) pronounced like the present tense verb of "leader" (as in "to lead"), or as in the toxic metal lead? Can you safely measure mains voltage using a multimeter set to 200Vac?
« Last Edit: May 11, 2012, 03:12:10 pm by dkl65 » Logged


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A fool can ask more questions in a day than a wise man can answer in a lifetime. - Aristotle
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Is that supposed to be offensive?
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No; it is not intended as offensive.
As far as I know It was never intended as offensive. Not by Aristotle nor by anyone else.
I see "fool" as "dummy" in the dummy books. (For your info that is "smart but not knowledgeable on the subject").
If you were really a fool -in the offensive way- you wouldn't bother asking the questions.

"A fool can ask more questions in a day than a wise man can answer in a lifetime." is a fact of life. Asking a question takes less time then responding. This is why a there is also "Choose your questions wisely" (I read that as "if you ask to many questions; people will stop responding").
Being on the answering side this thread demonstrates very clearly demonstrated the timing issue (to me) . That is why I wrote these famous words.
The side thought I had (and which is implied by the statement) is "I'm not going to investigate in continuing answering questions because it is going to ask to much time of me". (And now I find myself typing again  smiley-fat )

Best regards
Jantje

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So that means that I am connected to power plant via the water in the Earth? Sorry, grounding+insulation still has me confused (there is enough water in the Earth to conduct to the power plant?).

I take it google doesn't work on your side of the planet?

http://en.wikipedia.org/wiki/Ground_%28electricity%29

Also, why does my iPod charger release some sound that sounds like a cross between clicking and humming all the time when plugged in, and emits a high EMF measured by my Arduino EMF Detector, compared to other transformers (chargers)?

Cheap chinese manufacture? I'd definitely suspect the device is marginal in some manner; a switching powersupply may also make noises due to mechanical vibrations (generally cheap capacitors or coils).

Why are some plugs for appliances "polarized" (one lead bigger than the other) when AC is supposed to have no defined terminals?

Back in the bad old days (probably long before you were born - but then again, I don't know how old you are), a lot of electronic equipment and devices were plugged into wall outlets, and these outlets typically didn't have a ground pin (just two holes for the prongs) - just neutral and hot. Generally, the metal chassis of the device (like a radio or TV) was wired so that the chassis was at neutral. However, since it was possible to flip the plug around (or maybe the socket was mis-wired), you could have the hot be on the chassis. Normally, this wasn't likely an issue, unless someone was really unfortunate, and was touching some metal part of the device (like an exposed screw or something - remember, this was before a lot of the molded plastics and such like we have today), and the metal part (say the base of a lamp) that was plugged in properly (so it's metal parts were at neutral). Basically then the poor hapless fellow's body completed the circuit and ZAAAP!!!

There were various things tried to help correct this issue (grounded plugs, converters/adaptors, etc), but most had flaws, or were bypassed by people not understanding why they existed. So, eventually two things came about to help prevent this possibility of quick death:

1) Polarized plugs
2) Double insulation

Even so, people still manage to shock themselves - better idiots and such, ya know...

Is the word "lead" (as in leads (terminals) of a battery) pronounced like the present tense verb of "leader" (as in "to lead"), or as in the toxic metal lead?

Depends on the battery. Most of the time, you call the terminals, terminals. The term "lead" (as in leader) is generally reserved for wires or such (like those for a multimeter or other measuring instrument, or those that are attached to a discrete component, like the leads of an LED or transistor, etc). The term "lead" (as in the toxic metal) though, might be applied to a wet-cell lead-acid battery like you might find in a car, as the battery terminals of such a battery (and the plates inside) are made of "lead" (toxic metal), and generally so-too are the terminals on the ends of the battery cables!

Can you safely measure mains voltage using a multimeter set to 200Vac?

Yes - just be very, very careful when you do so.
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http://en.wikipedia.org/wiki/Mains_electricity
I think that I get how the power outlet in my house works. The small socket is at 0V potential (neutral), the big socket is a 60Hz sine wave of -110V to 110V and the round socket is connected to the Earth, as a safety precaution to lower the risk of electric shock, shorts, etc. (I think).
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http://en.wikipedia.org/wiki/Mains_electricity
I think that I get how the power outlet in my house works. The small socket is at 0V potential (neutral), the big socket is a 60Hz sine wave of -110V to 110V and the round socket is connected to the Earth, as a safety precaution to lower the risk of electric shock, shorts, etc. (I think).

The neutral is connected to the ground inside the breaker (fuse) panel, actually.
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