If you had a USB cord plugged into your computer and put the other end into your mouth, would it do nothing, give you a bit of a shock, or elecrocute you to death?
I never thought of USB cords as carrying that much current, but I realized my new cell phone can be charged via USB that’s plugged into either a computer or a wall socket (with an adapter). That makes me wonder if the USB cord I fling around so casually on my desk is actually carrying an equivalent punch to household current.
It’s 5 volts and 500ma. There isn’t enough current to do more than tingle a little, like if you licked a battery.
Ditto tingly. Nine volt batteries tingle enough it’s unpleasant; I guess a USB tingle would be much less uncomfortable. Not that 500 mA isn’t enough current to really mess you up; it’s just that you aren’t going to conduct 5 V well enough to draw much of the 500 mA, and you’re only doing it between points in your mouth.
Note that some line-powered USB chargers may have truely questionable design and construction standards (especially the $1 made-in-China ones). I would be careful about exposing my mouth to those.
A slight tingle less than a 9 volt battery to the tounge will result. This also goes for ethernet cables and phone
Although I understand that a phone cable carries quite a jolt when it’s ringing (up to 150 volts, from a quick Google).
Once long ago, when in a pinch I would use my teeth to strip phone wires, I grabbed a twisted pair of 20-gauge solid copper wire that I thought was loose but was actually live on the PSTN.
The 48V DC gave me a good kick (much more substantial than a 9V battery) and I wouldn’t want to do it again, but to be honest it wasn’t debilitating (more surprising). Of course the line wasn’t ringing–90V at 20Hz would be quite a different story I think.
Yes, it was a dumb habit and I don’t do it anymore.
I got zapped by a ringer once – had the modular jack in my teeth while changing the batteries in my answering machine, and I got a phone call in that 20 seconds. It was a real shocker, but it didn’t hurt at all.
I think you are more likely to be affected by the germs on the cable some time after sucking on it.
BTW, how well is the average motherboard protected against the USB socket getting shorted? It would be a question with all ports on your computer, of course, but with the number of things currently done through USB, and it simply being used as a 5V power source in some circumstances, it would seem more likely to occur. What happens on your typical system if you plug something into the USB port which creates a dead short across, ummmm … lessee … pins 1 and 4?
The USB standard requires built-in overcurrent protection. AFAIK, all ports are protected by a self-resetting 500mA fuse.
Napier made a key point here: the current isn’t flowing through your whole body. Even if a USB cable carried more than a couple of watts, the current would be passing through a centimeter or so of your tongue: not your heart or brain.
It does. Mine was when I was installing an extension when someone called.