Can 355 amps at 48 volts kill you?

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Jamesuk

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Can 24v at 355 amps kill you too?

Whats the rule vs volts and amps. I appreciate amps does the killing
 
I've been taught that under normal circumstances voltages below 48 Volt are safe to touch. Your body resistance is too high to to get any decent current going.
That doesn't mean you cannot suffer burns from sparking contacts or connection points with bad conductivity.

Just my 2cents
 
aluijten said:
I've been taught that under normal circumstances voltages below 48 Volt are safe to touch. Your body resistance is too high to to get any decent current going.
That doesn't mean you cannot suffer burns from sparking contacts or connection points with bad conductivity.

Just my 2cents
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The USA use 110v because that is regarded as reasonably safe under normal circumstances. 24v is way under that so will definitely not create sufficient current.

Richard
 
30 milliamps can kill. The issue is the resistance the body provides to the voltage causing the current flow. If you have wet salty hands then yes even 12 volts can give you one heck of a belt.

Ohm's law V=IR I=V/R R=V/I so 12 volts 0.03 amps R = 400 at 24 volts R = 800 at 48 volts R = 1,600

But electricity wil take the path of least resistance, and 330 amps at 48 volts R = 0.15 ohms. Putting yourself across this load effectively providing a parallel path will see virtually nil current flow through you.

BUT your biggest danger would be when the load is switched off (assuming this is an inductive load e.g. a starter motor). At that point the voltage could rise to many thousand volts, and the current flowing will then look at the available path ways at this induced voltage.

Now I suppose what I should have asked is, Why the question ?
 
RichardS said:
The USA use 110v because that is regarded as reasonably safe under normal circumstances. 24v is way under that so will definitely not create sufficient current.

Richard
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110 volts can be lethal, though the risk of fatality is not as great as a 240 volt shock. I have survived two 240 volt shocks which was down to luck and dry conditions. Where the US system scores is on 240 volt appliances such as cookers and air conditioners because they are powered by a single split phase system whereby each hot leg of the circuit is at 120 volts to neutral (or earth) and 240 volts to each other. That means that if you contact one of the live wires and are earthed, you receive a 120 volt shock, not 240 volts.
 
As superheat says the bodys resistance is what limits the current. You can't 'force' current into something, current is the by product of potential, voltage. The lower a circuits resistance the more current will flow through it, in proportion to the potential and limited at the top by the capabilty of the source. A truck battery, shorted out with a spanner will sink 3 or 400 amps easily, limited by the internal resistance of the battery itself.

As a rough generalisation your body presents about 10k ohms resistance. In normal circumstances 12v just can't drive any current into 10k. At 24v you can sense some current. 48 will give you a distinct belt. At 60v it starts to get into dangerout country.
 
superheat6k said:
But electricity wil take the path of least resistance, and 330 amps at 48 volts R = 0.15 ohms. Putting yourself across this load effectively providing a parallel path will see virtually nil current flow through you.
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The existence of any other path makes no difference at all: 48V will push the same current through you no matter what it's doing as well.

Norman_E said:
110 volts can be lethal, though the risk of fatality is not as great as a 240 volt shock. I have survived two 240 volt shocks which was down to luck and dry conditions. Where the US system scores is on 240 volt appliances such as cookers and air conditioners because they are powered by a single split phase system whereby each hot leg of the circuit is at 120 volts to neutral (or earth) and 240 volts to each other. That means that if you contact one of the live wires and are earthed, you receive a 120 volt shock, not 240 volts.
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Similarly, yellow site transformers are centre-tapped to provide two 55V supplies 180o out of phase, so tools see 110V but there is only ever a (probably) non lethal 55V r.m.s to ground.
 
Jamesuk said:
Can 24v at 355 amps kill you too?

Whats the rule vs volts and amps. I appreciate amps does the killing
Click to expand...

24 volts will not drive a high enough current through you to be fatal ....... a few hundred μA only in normal circumstances perhaps.


If you hang onto a high enough voltage to drive over 300 amps through you I'd think the result will be far more spectacular than merely fatal, but it will probably need hundreds of thousands of volts or more.


The rule between volts and amps through a simple resistance, which probably excludes the human body, is that amps are proportional to volts. Double the volts and double the current flows.


A little info https://www.physics.ohio-state.edu/~p616/safety/fatal_current.html
 
VicS said:
24 volts will not drive a high enough current through you to be fatal ....... a few hundred μA only in normal circumstances perhaps.
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24V can be fatal, but you have to be both wet and very unlucky indeed. Resistance from hand to hand, wet, is about 1 kilohm, so 24V can push about 25mA through you, which is just above what's required through the heart to do nasty things. Of course the full whack will not go through your heart, but if it's already a bit dodgy, enough might to set it off.

24V can certainly be felt if you're wet, and could be quite painful.
 
Lets not forget that main supplies are AC whereas batteries are DC.
So a mains supply voltage of 110 rms actually has a peak voltage of approx 110 x 1.41 (square root of 2)=155 volts.
The peak voltage will drive a peak current assuming a constant resistance and neglecting a couple of other things.(inductance and capacitance of the body for example)
So logic suggests therefore that in terms of effect on the body that the DC voltage should be compared with AC Peak voltage.

Is this logic sound?
 
The important thing here is the condition of your heart and the pathway the current takes to get from where you contact the potential and where you are earthed. Even 48 volts is capable of stopping your heart or severely affecting its rhythm, if you touch the potential with one hand and are supporting yourself against a good earth point with the other.

The large amperage you mention carries a different danger than electrocution though. Any electrical system capable of delivering the large current you mention in your question, would be capable of melting a spanner / screw driver / pair of snipe nosed pliers etc and spraying molten metal into your eyes.

I am curious to know what you intend doing which might require this research. I hope its not anything risky.

I have recently discovered that I can no longer use my chain saw, because the EM energy dissipated by the spark plug between my hands will cause my pace maker to malfunction. Anyone want to buy a chain saw?

Regards Chris.
 
Posts here have specified body resistance. However body resistance is a hugely variable thng. The outer dry skin tending to be insulating while the inner moist and bloodied parts tend to be good conductors. Hence we find in hospitals that electrical equipment is very carefuly checked for leakage curents and patients own (mains) elctrical devices are discouraged. Current through muscles causes convultions hence through the chest is very dangerous as it affects the heart. 24 volts aplied perhaps through a large area conductor with good conductive gel (think cardiograph pads) on the chest could kill. But generally on dry skin hardly felt. As said it is the 30 milliamps that kill. olewill
 
Norman_E said:
... I have survived two 240 volt shocks...
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Only two? My first was at age 6 when I climbed a ladder and grabbed a lighting wire, threw me across the room. I've had another half dozen since then, but the most recent ones have all had an R&D in circuit, the 30mA being chosen so as to not be lethal; it takes about twice that. The most painful was from 50V DC, not quite enough to fling your hand away.
 
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Adding to the discussion: When working in places with very high voltages around I was always told that a DC shock will make your muscles clamp on one way, so if you touch something live with the palm of your hand you won't be able to let go: touch the back of your fingers to it and the shock will pull your fingers away as the muscles clamp.
 
awol said:
Would you care to review that statement? I'm worried my shunt ammeter might read this and stop working!
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If you are silly enough to connect your ammeter across a 48volt supply it'll stop working ! If you are lucky it'll blow its own fuse , otherwise it will be toast.
 
VicS said:
If you are silly enough to connect your ammeter across a 48volt supply it'll stop working ! If you are lucky it'll blow its own fuse , otherwise it will be toast.
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Luckily the smart person who connected it put the shunt in the supply line from the batteries. My problem with the Duck's statement arises from a dim and distant memory of resistors in parallel.
 
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