# Electrical Safty C.W

#### Alireza

Hi Guys; as you can see I'm very new;)
I'm studying in Coventry University, and I need urgent help[b(]

I have to do a course work about Electrical Safty which I have no clue about it.

I was wondering if you guys can give me a link or some information about my question, it will be appreciated.

the main question which I have to write about it (around 100 worlds) is:

An automotive battery currently operates at a normal 12 V d.c. This voltage level is normally considered inherently safe. Explain why the automotive battery still represents a safty hazards.

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#### GENIERE

When charging, an automobile battery releases hydrogen gas. When “jump starting” another vehicle, connect positive terminal first and than connect to a frame member at some distance from the battery to avoid an explosion from possible sparking when the connection is made.

As far as electrocution, it occurs due to “cooking” via resistance heating, or by having sufficient current density passing through the heart. There may be nerve stimulation (let go threshhold)but I believe that is much less a factor as compared to alternating current in the 50-60hz range

A person’s skin resistance is the primary defense against electrocution. If one abrades the skin to remove dead cells, that resistance will be about 1000 ohms. It will be the same whether measuring from toe to finger or from digit to digit on the same limb.

What makes an automobile different from an old-fashioned carbon-zinc battery is that it has very low internal resistance. If a carbon-zinc battery of twelve colts is short-circuited, its high internal resistance will limit its current flow to several amperes, whereas the automobile battery can provide upwards of 300 amperes for a considerable period of time.

The most likely electrical hazard associated with an automobile battery, is to be burned by a tool accidentally laid across its terminals, which will be heated to high temperatures very quickly. Four or five batteries connected in series can be used to weld metals.

Skin resistance will prevent physiological damage to the body, by limiting current flow to the mili-amp range. There is only one possible way I can think of to electrocute someone. If a person has an exposed conductive path to the heart, as one might have during a medical procedure, the heart may be caused to fibrillate.

#### sheldon

WOW, I will make it short and simple. At higher voltage levels the electricity would be able to break down the insulation of your skin, enabling electrocution.

#### mmwave

Originally posted by GENIERE
If a carbon-zinc battery of twelve colts is short-circuited, its high internal resistance will limit its current flow to several amperes.
Let's see, 12 colts at about 1/3 horsepower per colt * 750 W / horsepower gives 3000 W. 3000 W at 12V gives 250 amps.

Seriously, a very good and thorough answer.
mmwave (who was almost knock off his horse by a colt today)

#### GENIERE

The Colt is a unit of electro-motive force honoring the famous Italian physicist, Alessandro Colta.

#### abdullah

<< duplicate post deleted by berkeman -- see abdullah's separate thread about safety issues >>

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#### berkeman

Mentor
berkeman said:
<< duplicate post deleted by berkeman -- see abdullah's separate thread about safety issues >>
abdullah, welcome to the PF, but we have strict rules about duplicate/multiple posts. The separate thread that you started with the same text that you posted here in post #6 is the correct place for that different discussion to go on.

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