My understanding of how HIDs work is that they are arc-lights in a xenon gas enclosure. Getting the electricity to arc accorss the spark-gap requires 20,000 volts and presumably enough amperage to indeed kill you. Since the alternator and battery cannot supply this amount of power, something called a "ballast" does it instead - from what I can tell, it's basically a big capacitor that can deliver a lot of electricity over a short period of time. Once the HIDs fire up much less electricity is needed because the gas is ionized, so the electrical resistance is much lower.

There are safeguards in place of course, but if you happen to be in the path of that ballast when it fires, I imagine you'd die.

There are plenty other ways to kill yourself with a car that don't have such warning lables, but I'd guess that people used to swapping out halogen bulbs might not realize the danger of working around HID ballasts, so the warning seems reasonable to me.

 

And they are right, too.

 

It's not the volts that kill you, it's the amps. You could have 50,000 volts course through your body, but as long as the amperage is not over 500mA, you'll probably live. There are many variables that can change this, especially if it's AC or DC current. The amount of AC current required to do damage is lower than DC. The reversal of polarity every cycle is the issue. This seriously disrupts the heart's beat.

 

yup, majored in electronics. we got zapped with 100,000 volts and it was nothing. but we had this little hand crank generator that would you up. amps are a measure of the power of the electricity. volts are a measure of how much force the electricity has behind it.

my teacher had a really good way of explaining it. think of a wire as a hose. the water flowing through it is electricity. the amps would be a measure of how much water is flowing out the hose. the volts would be measure of the force of the water shooting out.

haha, actually i just thought of another good analogy. for all you turbo guys, think of the amps as the CFM a turbo pushes, and the volts would be the psi.

 

volts is the number of joules per coulomb of electrons. A coulomb is 6.022*10^23 electrons, or one mole.

amps is the number of coulombs per second that are transferred.

Power is simply the volts*amps.

in your analogies, the current is dependent on the voltage (cfm is directly related to psi, flow is related to force). They are mutually exclusive in real life; adding voltage does not add current.

Decent analogies, I guess, but a more fitting description of voltage would be the TEMPERATURE of the water or air (as cooler air means more O2 molecules in a turbo, and cooler water is denser, too).

 

When you work around 1050 volt 150 kA arcs all day I think it is harder to get scared by silly little warning labels like that...

 

ok i know they weren't perfect, but i was trying to keep from geeking out on everyone. most people have no clue what joules or coloumbs are.

 

I tend to think of it this way:

AMPS is the measure of the number of electrons moving through the wire.
VOLTS is the measure of the force pushing those electrons along.

Anyway, one article I read says the HID bulbs require 1.75 to 2 amps during startup. Definitely enough to kill a person, isn't it?

 

actually, volts is a measure of the amount of power each electron is carrying.

 

Can you help me with my physics homework?