August 1st, 2005  

It's the current delivery capacity that hurts. I= current flow, E= voltage potential, and R= resistance to current flow.
I=E/R The wet tongue is about 1000 ohms of resistance. Braces are, for this purpose, 1 ohm of resistance. Solve for your tongue. I=9/1000 or .009 amps or 9 milliamps, won't even feel it. Solve for your braces. I=9/1 or 9 amps or the maximum that the battery is able to deliver to a short. Now heat produced in your braces is P=power, P=Isq x R or 9 x 9 x 1 or 81 watts of heat. 2 watts will burn your skin. Put that much heat on your most sensitive nerves, your teeth, and that, my friend, hurts. A car battery would have produced about 12 amps which would have fused the braces and turned them molten. 
August 1st, 2005  

Quote:
watchout, advanced subsidiary level physics LOL i think i got an E. If im lucky. 
August 1st, 2005  

Be very careful. 43 years of electronics engineering. The circuit path is from positive terminal to negative terminal of the battery. Or for electron flow theory from the negative to the positive terminals. Length of your tongue has nothing to do with it, at least not for this application. The measurement of conductivity is mho s. By the way, you'll be a bright kid someday.
