Which is more dangerous-alternating current or direct current?

[QuarkQuarkQuark2001]

Which is more dangerous-alternating current or direct current?

Is direct current only found in battery circuit but not the circuit which electricity come from power station?

[JaKiri]

AC is much much easier to generate in larger amounts, because you can make it through physical means (google for generators and the like).

 

DC is made by a chemical reaction (the combination of 2 chemical half cells, if you will) and so is much better for small scale applications.

[YT2095]

it depends how you define "Dangerous"?

if you`re considering it from a personal aspect of damage to Humans (animals) then DC is by far the most dangerous, as AC passes through a zero voltage phase, it allows some oportunity for you to be removed from whatever apatatus is electrocuting you, whereas with DC, your muscles will tighten making it difficult for anyone to remove you as your "grip" would be as strong as your muscles are capable of providing.

 

Hi frequency AC is a different story however, that will cause severe burns and deep tissue heating/damage.

 

(the above scenario is based on domestic mains and it`s DC equiv)

[QuarkQuarkQuark2001]

Oh I see.......

[MacM]

AC is used in power production and transmission in that it is much more efficient.

 

In DC you would actually push the electron down the line from the power plant to your house and through your computer.

 

In AC you merely jiggle the existing electrons in the wires. They move back and forth and it actually takes an electron hours to move from your wall outlet to your computer due to some intrinsic losses, etc.

 

Voltage is not dangerous but current kills. AC or DC current are dangerous. You can actually insulate yourself and hold onto a Van De Graff DC generator that charges your body to a million volts (I've personally done it to 250,000 Volts).

 

Your hair stands on end and your clothes move around as though you were in the wind but it is all static electricity. The trick is to discharge yourself "Slowly" and not create damaging current.

 

Or better yet don't grab hold of the generator.

[Primarygun]

I heard that 1.1-1.2 MA (not sure the amount) is the most dangerous to human body.

It is fatal to human. Less than 1.1MA, that have no problem for strong,healthy man.

Bigger than 1.2, the victims fall down and heart stops beating, but we can save him.

But I am not sure about the voltage,such as which amount is fatal.

[MacM]

I heard that 1.1-1.2 MA (not sure the amount) is the most dangerous to human body.

It is fatal to human. Less than 1.1MA' date=' that have no problem for strong,healthy man.

Bigger than 1.2, the victims fall down and heart stops beating, but we can save him.

But I am not sure about the voltage,such as which amount is fatal.[/quote']

 

I am not sure about lethal currents but the "MA" seems mighty low to me. It is also normally written in lower case i.e. - 1.0 ma. That stands for milli-amps. 1,000 ma = 1.0 amp.

 

My point however is (was) that it is the current and not the voltage that kills.

 

Voltage causes current:

 

E = I*R (Voltage = Current times Resistance)

 

I = E/R (Current = Voltage divided by Resistance)

 

Hence a perfectly insulated body (high resistance) suffers no current even at elevated (Millions) of volts.

[JaKiri]

It is also normally written in lower case i.e. - 1.0 ma.

 

He could always have meant megaamps, which would be really quite dangerous.

[MacM]

He could always have meant megaamps, which would be really quite dangerous.

 

I would think so.

[YT2095]

it`s all about overcoming skin resistance, a supply of 1 volt at a million amps will not kill you, it might just about power a digital watch (they use 1.5 volts generaly).

a few thousand volts at pico amps won`t kill you either (think static elec).

 

you MUST factor in the load (resistance) before making ANY calcs about power and lethality

[MacM]

it`s all about overcoming skin resistance' date=' a supply of 1 volt at a million amps will not kill you, it might just about power a digital watch (they use 1.5 volts generaly).

a few thousand volts at pico amps won`t kill you either (think static elec).

 

you MUST factor in the load (resistance) before making ANY calcs about power and lethality

 

The above numbers are grossly in error.

 

 

http://hypertextbook.com/facts/AprilDunetz.shtml

 

http://van.hep.uiuc.edu/van/qa/section/Electricity_and_Magnets/Electrocution/20020825144219.htm

 

http://www.csao.org/uploadfiles/magazine/vol11no1/shock.htm

 

This last one shows death at less than sufficient current to light a 100 W light bulb. At 120 V that means death occurs less than 13/16 of an amp.

[YT2095]

not at all, think about spot welders, a little under a volt and several thousand amps, you can touch both plates on the press with the power on without so much as a tingle, but it`ll melt a crow bar.

how do I know? we used to do it to scare newbies in the factory I worked at

 

edit: after looking at your links, it says "Goes Through" the body, 1 volt will not EVER overconme skin resistance even soaking wet

[Primarygun]

Oh very sorry for

You guys went into my trap

[YT2095]

what trap dude?

 

it`s Wattage (power) that kills, nothing more, nothing less.

it`s not volts or current, it`s the correct combination for a given resistance, it`s basic Electronics 101

[istok]

Hello,

 

Nikola Tesla proved that there is one thing called the "skin effect".

 

You see, if you have an AC current running through a conductor, such as a wire, then the current is not uniformly distributed in it (if you look at the cross-sectional area). On the surface of the wire, current density is highest. The more you go into the center of the wire, current density is weaker. For example, current density near surface is 1 A/m^2, and near the center of the wire it is 0,01 A/m^2.

 

The intensity of current decrement depends on one thing: the frequency of applied voltage. If the frequency of voltage is very, very high, then almost all of the currrent runs on very surface of the wire. As you decrease the frequency, more and more current is going to the center of the wire. At zero frequency, you have DC current and it is all uniformly distributed across the wire.

 

Actually, the current density falls exponentially with the frequency of applied voltage - in the direction of the radius of the cross-sectional circle of the wire. That explains all.

 

Well, since human body is also a conductor, then the same thing applies to it. If you have a current of very high frequency running through your body (e.g. 100 MHz), then nothing can happen to you no matter what the voltage is. The current is "only skin deep", it goes a milimeter of your skin in depth, and therefore it is not harmful to any vital functions, heart, muscles, and everythig else.

 

Tesla had several performances on various fairs proving this effect. He used to run million volts AC through his body, with very high frequency. And he always remained unharmed. Cute, isn't it?

 

Well, that should be the answer for you. Less frequency - more dangerous. But don't try it at home

 

Greetings from Belgrade, Tesla's capital

[YT2095]

excellent post! just to add a little to it though, voltage at frequency WILL cause RF burns! even at low power, 4 watts at 27 mhz (typical CB radio freq) will cause tiny blisters when localised, but no electrical shock, the higher the frequency the more surface the burn tends to be at the same power levels.

[istok]

the higher the frequency the more surface the burn tends to be at the same power levels.

 

Exactly. According to skin effect theory, this is happening because at higher frequencies all the current is "concentrated" in the skin surface.

 

Example: If 1 mA is running mostly through upper 1mm of your skin - at, let's say, 10 MHz, and no current runs beneath (this approximation is OK because of exponential nature of decreasing), than at 100 Mhz, the same 1 mA will be running through upper 0,01 mm. And that tiny surface of the skin is receiving a great amount of current.

[YT2095]

yup, 100% )

[pulkit]

I think the fact that you talk of certain amounts of currents being harmful is slightly incorrect.

At a given frequency of AC, a pearticular voltage would be enough to overcome skin resistance. If I recollect correctly, the normal household supply @ 50-60 Hz in most countries becomes hazardous at voltages beyond 120V, hence in several countries they prefer a 110V 60Hz supply.

DC voltages are not used primarily because of transmission problems, but they are exteremely harmful. Thats why one of its commercial uses is in electric chairs. But given that as already mentioned welding uses low voltages high current electric arcs, and DC currents of low voltages are often used for welding without any danger.

[ed84c]

 

DC is made by a chemical reaction (the combination of 2 chemical half cells' date=' if you will) and so is much better for small scale applications.[/quote']

 

or an AC input and a rectifyer..............(get one out of your radio if you want a look.....)

[pulkit]

or an AC input and a rectifyer.............

 

A rectifier is a very simple circuit and generally does not suffice to give very nice DC voltage, it has got lots of AC ripples. The simplest of rectifiers can be made of two or four diodes and give out give out input in the form of |sin(x)| (mod sinusoidal function). You need to use some filters to filter out the excess AC character.

[ed84c]

i think a NOT gate connected to an OR gate would work but you would still need a DC imput for the NOT

 

Also there is a components which removes 'excess ac character' i forget what its called but its used for other purposes as well (i forget what those are as well)

[ed84c]

and each gate being connected to a diode

[YT2095]

it`s really quite simple, imagine that 20 watts across the heart will kill you.

 

the problem is then what voltage at what current will be sufficient to overcome the natural avg skin resistance.

 

well Voltage will overcome resistance as it`s capable of jumping distances (arcs in the air, and air has considerable resistance!).

Current (Amperage) is the Amount of force the electricity has.

 

<yes this is incorrect terminology, and used as illustration only>

 

so imagine Voltage as speed (a ferrari) and Amperage as the bulldozer.

 

the volts may overcome the skin resistance (between 90 and 200k Ohms), but without sufficient current, the WATTAGE won`t be enough to kill (it may hurt like a b!tch, but not kill).

 

think Ohms law and then factor in the Power equasion, THEN and ONLY then, will you be able to determine what`s potentialy lethal or not

 

 

and yes, b4 anyone says it, I KNOW electricity travels at a constant speed, I DID say it was only an illustration!

[pulkit]

so imagine Voltage as speed (a ferrari) and Amperage as the bulldozer.

 

the volts may overcome the skin resistance (between 90 and 200k Ohms), but without sufficient current, the WATTAGE won`t be enough to kill (it may hurt like a b!tch, but not kill).

 

Excellent analogy drawn.