A King Kong Fled

[GrauGeist]

An interesting example of the conductivity of salt water versus fresh water:
If a vehicle drives into salt water, the battery will short out and fail almost immediately when it becomes immersed.

If a vehicle drives into fresh water (lake, river, canal, etc.), the battery will remain active until either the fresh water dillutes the volumn of sulfuric acid (electrolyte) or the battery becomes discharged (headlights on, ignition on, etc.)

 

[Shinpachi]

The circuit from the pole to the home is like this.
Sorry for my poor drawing

 

[mikewint]

Fumiyuki, my dear friend, first and foremost my most sincere desire that you and yours a safe from all danger from the recent earthquakes. Second your drawing is excellent. In the US nominal voltage is 120 volts and 60 Hz. While the CPS (Hz) are closely monitored and maintained the voltage varies with the load on the system. Electrical companies will even lower voltage under severe load conditions termed a "brown-out" here. The center tap transformers are the barrel-shaped objects mounted on the utility poles. Several customers can share one transformer. In general US homes receive 100 Ampere service provided by the two Line 1 & Line 2 taps. Electric stoves, water heaters, air conditioners, etc. use both lines or 240 volts nominal. Because of service brown-out possibility most of these will operate down to 208 volts. Electric ovens & water heaters will be slow to heat and air conditioners may not start or even burn out.
Center Tap Transformers
When an additional wire is connected across the exact middle point of the secondary winding of a transformer, it is called a center tapped transformer. The wire is adjusted such that it falls in the exact middle point of the secondary winding and is thus at zero volts, forming the neutral point for the winding. This is called the "center tap" and this central tap allows the transformer to provide two separate output voltages which are equal in magnitude, but opposite in polarity to each other. In this way, we can also use a number of turn ratios from such a transformer.
This type of configurations gives us two phases through the two parts of the secondary coil, and a total of three wires, in which the middle one, the center tapped wire is the neutral one. So this center tapped configuration is also known as a two phase- three wire transformer system.
In this way, half the voltage appears across one half of the phase, that is from line 1 to neutral, and the other half of the voltage appears across the next phase, that is from neutral to Line 2. If the load is connected directly between line 1 and line 2, then we get the total voltage, that is, the sum of the two voltages. This way, we can get more amperes of current at the same voltage.

Dave, water is a NON-CONDUCTOR. That may sound strange but is none-the-less true. The covalently bonded water molecules have no free electrons and only 1 in 10 million molecules will form ions. The purity of a water sample is measured by its electrical resistance. Pure water will have a resistance of a Megaohm or more. That being said water is seldom pure being a universal solvent. EVERYTHING dissolves in water varying only in degree of solubility. It is the impurities (ions) that allow conduction.
Fresh water has fewer, so more resistance to electrical conduction

 

[GrauGeist]

Dave, water is a NON-CONDUCTOR. That may sound strange but is none-the-less true. The covalently bonded water molecules have no free electrons and only 1 in 10 million molecules will form ions. The purity of a water sample is measured by its electrical resistance. Pure water will have a resistance of a Megaohm or more. That being said water is seldom pure being a universal solvent. EVERYTHING dissolves in water varying only in degree of solubility. It is the impurities (ions) that allow conduction.
Fresh water has fewer, so more resistance to electrical conduction

When we were kids, we'd run into the garage to grab a soft drink from the old fridge on a hot summer day.

However, if we had been playing in the pool, we would be soaking wet and grabbing the handle of the fridge would knock us on our ass. It never happened when we were dry (and barefoot), so the presence of water most certainly made it a challenge!

 

[mikewint]

Cool Dave, those old appliances were poorly grounded and often the chassis was the ground. We had an old house in which the conduit only had ONE wire in it. This went to the receptacle contact and a short wire went from the second contact to the electrical box itself. The metal conduit was the ground .
The body has resistance to current flow. More than 99% of the body's resistance to electric current flow is at the skin. Resistance is measured in ohms. A calloused, dry hand may have more than 100,000 Ohms of resistance because of a thick outer layer of dead cells in the stratum corneum. The internal body resistance is about 300 Ohms, being related to the wet, relatively salty tissues beneath the skin. The skin resistance can be effectively bypassed if there is skin breakdown (burn) from high voltage, a cut, a deep abrasion, or immersion in water. The skin acts like an electrical device such as a capacitor in that it allows more current to flow if a voltage is changing rapidly. A rapidly changing voltage will be applied to the palm and fingers of one's hand if it is holding a metal tool that suddenly touches a voltage source. This type of contact will give a much greater current amplitude in the body than would otherwise occur.
At 500 V or more, high resistance in the outer layer of the skin breaks down. This lowers the body's resistance to current flow greatly. The result is an increase in the amount of current that flows with any given voltage. Areas of skin breakdown are sometimes pinhead-sized wounds that can be easily overlooked. They are often a sign that a large amount of current could enter the body. This current can be expected to result in deep tissue injury to muscles, nerves, and other structures. This is one reason why there is often significant deep tissue injury although little in the way of skin burns with high-voltage injuries.
It is interesting to note that:
1mA is a barely perceptible current
16mA is the maximum current an average man can grasp and still "let go"
20mA will paralyze the respiratory muscles
100mA will cause Ventricular Fibrillation
2 A will cause Cardiac arrest and cause major organ damage
Common circuit breakers trip at 15/20 Amps

 

[bobbysocks]

yes it isnt the volts that get you. we used to have a static generator in science class where we would run several thousands volts through a circle people. the large lines push a lot of amps through them.

we see this all the time both at home and at my cottage...mostly after storms when branches cross lines...the second one is even more dramatic at the end


View: https://www.youtube.com/watch?v=g4ph-h7l_aM



View: https://www.youtube.com/watch?v=aoeTTbgCIfY

 

[mikewint]

Bobby, true and not true. A typical lighting bolt is about a billion volts and perhaps 200,000 amps.
Basic electricity: VOLTS X AMPS = WATTS. Where Watts is a unit of power. 1 Watt is 1 Joule per second and 746 Watts is One Horse Power
OHM'S LAW - VOLTS = AMPS X OHMS (total resistance)
OK, now:
For currents above 10 milliamps, muscular contractions are so strong that the victim cannot let go of the wire that is shocking him. At values as low as 20 milliamps, breathing becomes labored, finally ceasing completely even at values below 75 milliamps.
As the current approaches 100 milliamps, ventricular fibrillation of the heart occurs - an uncoordinated twitching of the walls of the heart's ventricles which results in death. Now as weird as this may sound above 200 milliamps, the muscular contractions are so severe that the heart is forcibly clamped during the shock. This clamping ia actually a "good" thing as it protects the heart from going into ventricular fibrillation, and the victim's chances for survival are good provided CPR is immediate.
So basically it's power that kills, or better yet, current through vital organs which depends on the current capacity of the source and its voltage (and the needed voltage depends on the resistance through the body which again depends on the skin condition and so on). That's why you don't get killed by static electricity discharges that can go into tens of kilovolts easily and why it's dangerous to touch both terminals of a 12 V car battery.
Now the human body -
Under dry conditions, the resistance offered by the human body may be as high as 100,000 Ohms. Wet or broken skin may drop the body's resistance to 1,000 Ohms, however high-voltage electrical energy quickly breaks down human skin, reducing the human body's resistance to 500 Ohms.
Thus 1 Volt and 0.1 Amps cannot injure since 0.1 Amps would require 10,000 Volts to go through dry skin or at best 100 Volts through wet or broken skin. Now with household circuits, essentially 110 Volts and dry skin resistance approximately 0.011 Amps or 11 mA will flow, not enough to kill but a good zap.
DC or Direct Current. Consider the automobile, a 12 volt DC system. A 500 Watt starter motor requires 42 Amps no load and probably 10 times that in cold weather. That same motor powered by 110 Volt AC requires only 4.5 Amps. That's why automotive wires are so much thicker and heavier than household wires. A good car battery could easily be rated at 800 Amp-hours, i.e. supplying 800 Amps for 1 hour or 400 for 2, etc.
DC current will cause a single continuous contraction of the muscles compared to AC current, which will make a series of contractions depending on the frequency it is supplied at. In terms of fatalities, both kill but more milliamps are required of DC current than AC current at the same voltage. Either AC or DC currents can cause fibrillation of the heart at high enough levels. This typically takes place at 100 mA of AC (rms, 60 Hz) or 300 – 500 mA of DC.
More basic Electricity: An Ampere of current is 1 Coulomb of charge per second or 6.2 X 10^18 electrons flowing every second.
Ok back to Static Electricity. The Human Body can and does act as a capacitor and thus it "stores" electrons. This capacitance is in the range of 100 – 200 pF (pico-Farad)(pico- trillionth of a). A 1 F capacitor (a very large amount) stores 1 coulomb at 1 volt of potential. So the low human capacitance means that large potential differences (+25,000 volts) can easily develop but few electrons are stored thus when discharged very little current flows.
Let's put it all together:
Resistance of dry skin is 100,000 Ohms plus in order for there to be a spark, there must also be air between you and whatever. Air is a bad conductor and must be ionized. Let's guess that we have 10 MOhms (= 10,000,000 Ohms, or a hundred times as much as your hand) of resistance there.
Current = Voltage / Resistance = 20 kv / (10,000,000 + 100,000) Ohm = 0.002 Amps.
Current moves through a resistance if there's a voltage. Because there are two resistances, the voltage is shared between your hand and the air gap. Turning the above formula around a bit, we have:
0.002 Amps * 100,000 Ohms = 200 Volts
inside your body and the rest (most of the 20,000 Volts) across that air gap. So actually, most of the power of the discharge is heating up the air, not you.
Now the BIG deal: there is no steady supply. Static electricity is a stored quantity of electricity without a backup supply to keep it coming. Those few trillion electrons you ripped off are just a drop in the bucket, energy-wise, and once they jump off your finger and into whatever, they're gone, the potential difference is used up and goes back to 0 Volts. A spark crosses over in a very small fraction of a second, so it's able to deliver enough power to sting a very small patch of skin (mostly by direct nerve stimulation) but not to burn anything.

 

[Old Wizard]

It's nice living in a newer part of the city. All wiring is underground and the transformers are in green boxes on the ground.
No ugly wires.

 

[mikewint]

AND a much lessened chance of a outage due to weather, trees falling, cars hitting poles, etc. Our wires here are still on poles but are underground to the house

 

[Old Wizard]

Of course, we still get outages when a transformer station gets hit.

 

[bobbysocks]

nothing like watching a transformer blow. just like the 4th of july but a lot closer to the ground....

 

[mikewint]

Happens here as well, generally due to lightning or squirrels who seem to love chewing on insulation.
Not here but back in Illinois, the Morris tornado took out two high voltage distribution towers which was even MORE spectacular!

 

[bobbysocks]

yeah...I will bet that was spectacular. we had a 'nado go through up in the mountains. took down the kinzua rail bridge. it wasn't used except for tourist rides. bend the crap out of it...they salvaged a part and made it a look out point.