Why can a 120V outlet kill you while a 25,000V taser won't?

Question

I know current kills you, not voltage, but V=IR, so shouldn't R be the same for your body in both cases? Wouldn't that make the current much much higher for the taser?

Answer 1

You are correct in thinking that Amps are what generally kill you.

However, whilst an taser is delivering so many volts, it is designed to only be able to deliver a very low current, by having a (relatively) small capacitor and battery. The limiting factor is the amount of Power (P = Amps * Volts) stored in them (in the region of mW [milli-Watts], I believe [research this, it may be less!]), so when taking a high voltage, only a low amount of current is produced.

An outlet, however, doesn't have the same limiting factor as a taser... because it can supply hundreds of Watts of Power at 120V, resulting in much larger currents produced.

Answer 2

Charge is about 3 milliamps, therefore there must be a high resistance in the weapon.

Answer 3

Actually, voltage and resistance are the determining factors for how much current will flow through a circuit.  Amperage can't exist on its own...it's a DEPENDANT variable.

In most real life circumstances, the formula you would use is Voltage\resistance = Current.  (Voltage divided by resistance = Current.)  

For example, if we look at a high voltage power line, we can't point to it and say "There are X number of Amps there."  The amount of current flowing through the line will depend on the load and varies widely.  However, we do know the voltage.  Let's say it's a 15,000 volt distribution line.  The reason why a taser won't kill you, but a high voltage power line will is because a power line is capable of supplying a massive amount of POWER.  People mistakenly say "volts don't kill you, it's amps."  But the fact is that it's BOTH.  If you come in contact with a high voltage power line, there is nothing to limit the current.  Whereas a taser can only supply a very small amount of current to begin with because it's drawing its power from a battery.  It's true that ultimately it is the current that causes damage, but the amount of current that will flow through a circuit (or you if you are unlucky enough to get electrocuted) depends on the VOLTAGE and the resistance of your body.  

I'll give you another example.  A 12 volt car battery can supply hundreds of amps.  But if you touch the poles, and as long as your hands are dry, nothing will happen.  This is because the voltage is too low to overcome the resistance of your body.  I'll go grab jumper cables right now if you like.  But if you try that with 120 volts, the shock may be lethal.  Note that it doesn't matter whether the current is AC or DC, the determining factor is the voltage.

Also, people mistakenly think that high voltage always has to mean "low current."  Not true.  A neon sign transformer or microwave oven transformer will supply both high voltage and high current.  They're great for doing high voltage experiments, but also very dangerous if you aren't careful!

This is why everything is rated in VOLTS.  When you buy a power adaptor (for your cell phone recharger, printer, etc) they always give the rating in voltage and polarity.  The amount of current that will flow through the circuit depends on the load.  And that depends on the resistance.

The reason why a 120 volt outlet could kill you, but a taser can't is because an outlet is capable of supply more power.  There is nothing to limit the current except a blown fuse or a tripped circuit breaker.  And if it wasn't for fuses or circuit breakers, then a short would cause the wires in the house to overheat and melt, or maybe the transformer on the pole would overload and eventually shut down. A 25,000 volt taser won't kill you but a 25 kilovolt power line would instantly kill you...after causing severe burns.

Answer 4

Amps kill you, not volts

Answer 5

You are right, Amps are the thing that kills! You quote V=IR, which if you assume R is constant then if you increase the voltage, the amps would normally go down, not up.

However that only applies on a specific source, for a given load, so if your voltage reduced your load would need more Amps to run.

With the taser example alongside the 120V outlet, they are independant, which means that the votage and current can be set at whatever they like. There is for example no reason why they couldn't make a 5Amp, 25kV taser, except that it would kill.