It's The Amps

Post date: Jun 15, 2012 5:20:31 AM

There's an EE (Electrical Engineering) Idiom "It's the Amps that kill you."

I stumbled across a post over on the science forum where someone called that a play on words and claimed that categorically it's the voltage. I was so enciced that I created an account on the science forum to dispute. Then I decided that was a little ass-hatty and refrained however I have too much to say on it so I'm posting it here.

Technically and specifically it is the current (amperage) flowing through your body that does the damage. It is entirely possible for a human body to hold a charge in the thousands of volts without feeling any ill effect other than frizzy hair. In fact it's not even uncommon. We call it static electricity and notice it when we get really close to some ground source like a door knob and just before we touch it the tremendous voltage in our body passes the breakdown voltage of air converting it from an insulator into a conductor and creating that tiny (and painful) arc between us and said ground.

I think Mr. Stanley514 was trying to make a good point I just don't thing the way to correct a slightly innacurate statement is by making a wildly inacurate stagement.

I like to phrase this idiom "it's the amps that kill you.... But the voltage helps."

As someone else points out in the above post voltage, amperage and resistance are all directly related. So when stanley514 says "this is just a play on words." he's correct. Because it's a WHOLE LOT easer to be killed by high voltage than by low. The idiom exists for two reasons. One, because it's technically true and was probably coined by an OCD engineer. Two, to remind you to pay attention you can be seriously injured by voltages down as low as about 5volts and killed by stuff around 9 or 12. You know those painfull assed gag toys that look like a stick of gum but shock you? those run on 1.5v.

Thing is, it's like being hit by a car. The car has mass. That's your voltage. it's not the mass of the car that's hurting you. You can stand up against a parked car without being injured in any way. it's the fact that, that mass is hurtling towards you at 40+ miles per hour when it strikes you that smears your brains all over the wall. I could kill you with a trycycle if it was moving fast enough. Bullets, for example weigh about as much as a pencil. I don't think anyone would deny that when they hit a human body at several hundred feet per second the effect is someone dramatic.

The thing is if I throw that bullet at you pretty gently. Say it's travelling at about 20 miles per hour. it just might sting a tiny bit if you're real sensitive. If I smack you directly in the eye it might even hurt. Now, imagine being hit by a semi at 20 miles an hour. That could, quite possibly be fatal.

Tt's not the mass of the thing hitting you that kills you. Yeah, well the mass helps.