I haven't found the time to work on the cord. I will now.
Someone please explain why do some modern factory drills, grinders
and saws get away without a ground plug?
Older style equipment has only one layer of insulation. A *single* failure
exposes the operator to electrical shock, unless the equipment is properly
grounded. With the grounding, it requires _two_ failures for possible
shock.
Newer gear is constructed in a style called "double insulated". It takes
_two_ separate "safety equipment" failures for the operator to be exposed
to a possible electrical shock.
By the nature of the 'double insulated" design, a failure of the second
insulation is much *less* likely than a failure of the 'grounding' system
in older equipment.
Hence safety is provided for in a "more reliable" manner. and the 'ground'
plug is not needed -- it doesn't provide any 'additional' protection.
(Here's an ignorant question) Is it true that I can receive a fatal shock if
I touch my skin from either neutral or hot and then ground?
Short answer: "Yes, you _can_ receive a fatal shock that way." This is not
to say that it _will_ be fatal in every instance. (see the 'long answer',
below, for all the gory details.)
Long answer (bear with me, it _does_ take a *long* discussion to cover all
the relevant matters) follows --
That's a *complicated* question. First off, what constitutes a "fatal"
shock depends on a _lot_ of things. The absolute minimal considerations
are 'how much _current_', and '*where* on the body'. applied directly
to heart muscle, a handful of milli-amps, which requires only a few volts,
is sufficient to cause 'catastrophic' problems.
Applied to the skin, away from the heart, what constitutes a 'dangerous'
level requires higher levels.
"How much" higher depends on a lot of things. The 'resistance' of skin,
etc. depends on a whole sh*tload of factors., but the biggest one is
how _dry_ the skin is, where contact is made. On a living being, "dry on
the surface" skin has a resistance of several thousand ohms. When skin is
damp -- sweaty, for one example -- the resistance decreases radically.
Can be as low as a few hundred ohms. _Below_ the surface of the body,
resistances are quite low. *especially* so for 'nerve fiber', which
runs *everywhere*.
Now, we have to take a digression into 'how electricity works'.
(note to purists: this description *is* somewhat simplified)
When you have two things "in parallel" connected to a source of electrical
power, There is always a flow of electric current through *both* of those
things. "How much" current flows through each thing is determined by the
resistance of that thing.
Note: 'in theory', "ground" is "ground", and is always at exactly the same
potential, regardless of location. In practice, it doesn't work that way.
"Ground" is a moderately lousy conductor, and you may get different levels
at different places.
In addition, the 'ground' and/or 'neutral' wires are *not* "perfect"
conductors. They are real-world devices, and have 'internal' resistance.
Depending on the size of the wire, and the length back to the transmission
point, this resistance can be significant. Any piece of wire, when you
connect to it at a point along its length, can be regarded as two resistors,
one representing the internal resistance from the beginning to where you
connect to it; the other from that connection-point to the other end of the
wire.
This means, among other things, that the 'neutral' wire _at_a_point_distant_
_from_the_power_source_, is *not* at the same 'ground' level as 'ground' at
the transmission point.
If you connect your body across the 'hot' wire, to ground (either 'earth
ground', or the 'ground' wire), you are placing yourself "in parallel"
with any other 'devices' (or 'loads') on that power feed. As those devices
have relatively high resistances (relative to 'just plain wire'), there
will be a considerable flow of current through your body.
If you connect your body across the 'neutral' wire, to ground (either 'earth
ground', or the 'ground' wire), you are placing yourself "in parallel" with
only the resistance of the 'return' part of that wire. This resistance is
comparatively _low_, and the current flow will be comparatively small.
From all this, it should be obvious that there is no simple nor easy means
of predicting "just how much" current _might_ flow through your body if you
get across the wires.
One more consideration to throw into the pot. There is no 'guarantee'
that the 'hot' and 'neutral' wires are _properly_ connected/identified.
What one _thinks_ is th 'neutral', may, in actuality, be the 'hot'.
It's not likely, but do you want to "bet your life" (literally!) on it?
The only "safe" way to work on electrical wiring is to:
0) assume that unprotected contact with the wiring *will* kill you.
(even if not _always_ true, you only get to be wrong ONCE )
1) disconnect it from the power supply
2) ensure that *nobody* can re-connect it without your OK.
(this is what "lock-outs" are for.)
3) test _after_ disconnecting to make sure there is no power present.
4) work on it *as*if* power was still present. (see rule #0)
(i.e. rubber gloves, insulated tools, only one wire at a time, etc.)
While that may _look_ excessively paranoid, it isn't.
Items 1,2,3 'appear' to describe a 'fool poof' system for ensuring safety.
Unfortunately,
"For every fool-proof system, there exists a *sufficiently*determined*
fool capable of breaking it."
applies.
that's why 4 *is* necessary.
If so, then why
not replace the ground with a safer model which doesn't allow a shock?
That's what modern "double insulated" tool design _does_.
That is *why* most tools are built that way today. <grin>
As for "doesn't allow a shock", well, the laws of physics are not subject
to repeal by the acts of man. ANY place there is a difference in electric
potential, there is the 'potential' for an electric shock. (Pun intended!)
The most one can do is engineer things so that getting a shock is "difficult".
Lastly, a hot or neutral short to ground shuts down my entire electrical
system. Is this the GFCI?
Probably.
GFCI detects _unbalanced_ current flow in the hot vs neutral wires.
This happens *only*if* there is 'some other path' for current to flow
through.
In the case of a 'hot to ground' short, assuming it is a true short (as
in approximately zero resistance), it will be a bit of a race between
the overload circuit breaker, and the GFCI, to see which trips first.
In the case of a 'neutral to ground' short, you do not have an 'overload'
condition, so the GFCI is the one shutting things down.