They are more properly called “arc flashes” or “arc blasts.” By far and away the greatest damage from these is due to heat; enough to cause third degree burns over an entire body almost instantly. Click here to see actual security camera footage which caught a large arc flash incident as it happened. It is of note that the greatest risk of arc flash occurs at the 480-600 V level (typical of what I work around daily)–much below that AND much above that, the amount of energy released is significantly smaller.
I just had to revisit this…
Actually, you are driving the tube with half your power.
The current across the tube is, in effect, just the top have of the sine waves (slightly flattened out with capacitors, I believe). The current looks sorta like the humps the Loch Ness Monster makes in the water (only closer together because it’s multi-phase).
In any event, it’s not the flat line you see from pure DC.
Ok. I’ll go now.
Not with a full-wave rectifier - You get to use both halves of the cycle.
You could be right, there. I was talking to the BioMed guys (the guys that fix the machines when we break 'em), and may have gotten the description wrong.
So, tell me…with three-phase, fully rectified AC, what you end up with, in effect would be 6 “humps” of overlapping, rectified AC per cycle across the tube, right?
Indeed. My old Steadicam systems used a Raytheon high-voltage C.R.T. The D.C. battery that drove the system was 14.4 volts, and was rated at about 5 amp hours.
The tripler circuit, with which I became intimately familar with a few times, ran that up to 18,000 volts D.C. I might opine that “tripler” is the understatement of the century. When the voltage “leaked” out of the high-voltage white silicone cable that ran right into the C.R.T. tube itself, it produced little pretty but intense lightning bolts from the cable to the metal housing of the monitor.
The proper fix was to replace it at great cost. The street fix was to take a watercolor brush and G.E. brand 100% silicone in a tube from the hardware store. Brush in a thin layer over the tiny crack, dry with hair dryer from Hair & Make-Up. Repeat many times. Last layer, leave damp, wrap with black electrical tape. Go back to work. 
Ouch.
Cartooniverse
Right.
Never saw it kill, just almost kill.
What are the odds of being hit by lightning twice and surviving?
Shrug;;;; You are prolly right but I am not going to try it even though you poo poo it. You willing to lay it on the line since you are so sure? You willing to bet that your internal resistance is alway at least 1000 ohms or better at all times.
I can do an EIR triangle too
Carry on, you da authority…
Underlinining mine. Aha moment. So when people design radios and clothes irons and such, they choose a wire or other conduit that A) will carry enough current for the appliance to work, but B) not carry too much current and fry the appliance?
I wonder if you could get killed with a Prius or other hybrid that has multiple batteries. Blood has electrolytes, and the hemoglobin has iron. But, my ignorance on the subject has already been well established.
Not really, no. Simply put, a wire provides only resistance (which often has to be factored in). A power supply is typically designed as a voltage source – as in it will provide somewhere around X volts (let’s say 12). Your circuit determines the resistance, which will determine the current.
If an appliance has a certain resistance, and a power supply provides a certain voltage, there is no way from pushing any more or less current through the circuit of the appliance than the voltage of the power supply divided by the resistance of the appliance. Your wire’s resistance is only added to the total circuit resistance.
(I’m disregarding any dynamic properties, impedance, etc.)
In other words, think of electricity as something that a circuit takes from a power supply, rather than something that is put into the circuit. The power supply (like a battery) makes it available at a certain voltage, the circuit takes what it ‘needs’. The only way you fry something is if you provide higher voltage at the power supply, which for the same resistance would increase the current in the circuit.
Actually, C) will safely carry the maximum current the device is expected to draw without overheating and presenting a fire hazard.
The resistance of the human body with direct blood contact is fairly low. I’ve seriously burned myself when terminals from a 2.4V (2x AA NiMH) battery pack pierced the palm of my hand about an inch apart. It burned a path between the terminals in my hand. I have no scar, but I’d say that I wouldn’t risk even a 2.4V 2x AA batteries across the heart, even if it’s all the way hand to hand. Tiniest currents, under 1ma can kill you if they go directly across your heart. Most of the studies you’ll find assume intact skin, and underneath it you’re just a giant bag of electrolyte.
Yes.
This is the “concern du jour” about hybrids. The battery packs in the Prius output 240v, which is easily enough to kill you. I believe that there are safety interlocks that disconnect the battery in the event of a crash, but there is still concern for first responder’s safety - if they need to cut into the car to free an occupant, they don’t want to be cutting into the high voltage cable.
FWIW, anything below 50V is usually considered a safe working voltage, most applications are able to keep the ‘finger-safe’ voltage much lower though. In safety courses I’ve heard them give the lowest known fatal voltage as 42V but I’ve never seen a cite for that. I regularly measure voltage leaking to ground at >10V, especially on older equipment. Newer machinery, in our mill, has better bonding but that’s more to protect the bearings than the operators; I still see some leakage between the equipment ground and earth ground (the grounding grid of the building). As you say though, small batteries can create a lot of current which many people under-estimate. A co-worker was pulling a 3.6V battery from a UPS and it was stuck, not thinking he grabbed it with his needle-nose pliers which shorted it out, we were quite amazed at how quickly the ground wire burned up, it was 12 gauge wire.
So rather than thinking of the outlet pushing power to the appliance, it’s more like the appliance pulls it out of the wall? But really, electrons will follow the conductors as far as they go…that ends at the outlet, until you plug something in. The appliance may have an on/off switch that completes or breaks the circuit for its design, of course, but you wouldn’t want to work on an appliance that was plugged in, even if it’s switched off, because the electricity is already inside it. Right?
I think of “resistance” and “impedance” interchangeably. What’s the difference?
Impedance is a characteristic comprised of the complex sum of DC resistance and AC reactance (“resistance” of reactive components like inductors and capacitors). Here, the current and voltage are not necessarily in phase.
Thinking of them as roughly equivalent is not too bad as far as basic understanding goes.
Well in an appliance that is turned off but plugged in, the circuit is energized up until the On/Off switch. I wouldn’t say “electricity was already inside it”, but rather “I don’t trust that part of the circuit to not kill me.”
In simplest terms I can come up with, impedance is the extension of the concept of resistance to AC and typically is represented by a complex number with the real part being simple resistance and the complex part being relative phase difference between voltage and current.
Right. Assuming there are many and complicated circuits in it, you don’t know where it’s already holding some current.
I’ll have to mull this. Impedance is measured in ohms on my stereo stuff. Resistance is measured in…?
Well it’s not holding current. If it’s really off, it’s off – there should be no circuit. What you don’t want to do is to inadvertently complete the circuit with your hand or some tool.
Ohms. Impedance is a complex number of ohms though 
They’re both measured in Ohms and they both represent opposition to current flow. The resistance is a component of impedance but the impedance also includes opposition caused by reactance (capacitors and inductors). The effects of reactance are mostly applicable to AC circuits though they are a factor in fast-switching DC circuits, basically any time the voltage or current are varying.
As far as how to think about the device in relation to the power source just think of the electrical station that produces your power as a giant pump, essentially they’re pumping charge through your wires and your device. For an AC supply the electrons don’t really go anywhere, they just vibrate back and forth. If you open the switch supplying the device, the power station can no longer pump the charge through the device.
Since nobody’s addressed this yet: First of all, AC current isn’t a stream of positives and negatives going the same way; it’s still just electrons moving, but they’re moving sometimes one way, and sometimes the other.
Second, AC does need a return path. No individual electron will ever make it all the way around the circuit (the electrons themselves are travelling way too slow for that), but electrons all along the wire are jiggling back and forth. If you just had one wire and ended it, the electrons at the end wouldn’t have room to jiggle, and because they weren’t jiggling, the next electrons over wouldn’t have room to jiggle either, and so on down the line.
The reason why AC is used instead of DC for power transmission is that losses from the resistance of the wires increases with the current. For a given amount of power available, you can increase the current by decreasing the voltage, or vice-versa. So for long-distance power transmission, you want a really high voltage, so you’ll only have a really low current, and therefore low losses due to resistance. Where AC comes in, is that making that tradeoff between voltage and current is a lot easier with AC than it is with DC.