# Electricity and the shortest path

1. May 14, 2004

### ShawnD

Why do people die when a radio falls into the tub they are bathing in?
The wires only have a voltage relative to each other. Red has voltage relative to black, but not the water or the person. Black has voltage relative to red, but not the water or the person. Electricity always follows the path of least resistance, so shouldn't the electricity go straight between red and black instead of going through all the water and the person?

2. May 14, 2004

### enigma

Staff Emeritus
Electricity follows all paths. More current flows through the lower resistances, but some flows through all of it. Additionally, the black is just ground... the same as the pipes and the tub. To make it worse, you short circuit the plug, so you're pulling between 15 and 20 amps... usually 20 if it's a bathroom fixture that isn't GFCI or AFCI protected.

3. May 14, 2004

### Chen

When you connect two resistors of different resistance in parellel, will current only flow throught the resistor with lower resistance?

I is proportional to 1/R, and the resistance of "all the water and the person" is simply not high enough to make the current neglible. And I guess the reason they die is that they don't have time to climb out of the bath tub before the electric shock becomes critical, because as far as I know you lose most control over your muscles in these situations and they contract themselves. That's why when you touch a lamp, for example, to see if it's dangerous, you should touch it with the back of your hand rather than grab it. But I may well be wrong.

4. May 14, 2004

### krab

They don't. It's a myth created by Hollywood. It's similar to the myth that you can electrocute someone with a car battery.

5. May 15, 2004

### pallidin

What??? You can't be serious.

6. May 15, 2004

### ShawnD

What would make you doubt Krab? He's always been right before.
Everybody knows you can't shock somebody with a car battery, but the radio in the bathtub thing is somewhat believable.

7. May 15, 2004

### pallidin

The car battery situation I understand. My gripe is with the radio, like you suggested.
My wife has a hair dryer in our bathroom which has a "Do Not Remove" tage on it. The tag has a drawing of a bathtub and a hair dryer above it and a big red X over the entire pic. The text on the tag says :To Reduce Risk of Electrocution Do Not Use Near Water"

8. May 15, 2004

### Chen

Kill you or not, I doubt it's in your best interest to throw any electric device into your bath tub.

9. May 15, 2004

### ShawnD

Throwing a radio into the tub will probably trip the breaker before it has a chance to do any real damage.
If the break doesn't work properly, your house will probably start on fire

10. May 15, 2004

### Gokul43201

Staff Emeritus
You can die if you have 20 amps go through you. But in the bathtub, most of the current will pass through the water (R~L/A, or think of it as the potential gradient across your body being small compared to some of the water near the electrical leads). So, even if you short the supply without tripping a breaker or fuse, you're only going to get badly zapped, at worst.

Note that this is very different from sticking metal wires into a the sockets of a power outlet - though if you hold both wires in the same hand, like chopsticks, you may only end up with a toasted hand.

Please don't try any of these things cause they are all extremely dangerous, and most are exceptionally stupid.

11. May 15, 2004

### ShawnD

I actually stuck things in the wall before when I was like 5. Knife in either side then touch em; youch! Hopefully it didn't fug my heart.

12. May 15, 2004

### KingNothing

Yeah, I tripped the circuits 3 times within about a year when I was little, nearly electrocuting myself, and understanding better than most at an early age how electricity works.

13. May 16, 2004

### pallidin

OK, let's do an experiment to find out.
First, let's get our hands on that ******* who beheaded Daniel Berg in Iraq. (BTW, I saw the ENTIRE video of the execution... most disturbing)
Next, lets give that ******* a bath since he likely hasn't had one since he was born.
Then, let's put in some pretty pink bubble soap just to piss him off.
Now, let's throw in a live connected radio, hair dryer AND T.V. and see what happens.
Of course, as good scientists, we will want to repeat the experiment several times.

14. May 16, 2004

### ShawnD

In that experiment, if you used big wires and no fuses/breakers, the water would probably boil and he would die from the heat.

15. May 16, 2004

### Pierre

It is far from a myth created by anyone.

The breaker wil not trip (unless it is a groung fault breaker those with reset on it) and you are not only die but you will die cook.