Transcript Ohm`s Law and Electric Shock

Ohm’s Law and Electric Shock
What causes a human body to be
shocked…voltage or current?
 The electric current in
amperes is the most
important variable which
determines the severity
of an electric shock
Will the 120 volt common household voltage
produce a dangerous shock? It depends!
 If your body resistance is 100,000 ohms, then the
current which would flow would be:
 But if you have just played a couple of sets of tennis, are
sweaty and barefoot, then your resistance to ground
might be as low as 1000 ohms. Then the current would
be:

 The severity of shock from a given source will
depend upon its path through your body.
Bird on a wire
 A bird can sit on a high-
voltage wire without harm,
since both of its feet are at the
same voltage. (There must be
a difference in potential
between one part of its body
and another part.
 You can also see that the bird
is not "grounded" –
 You will not be shocked by
touching a high voltage if
there is no path for the
current to reach the Earth or a
different voltage point.
So sad
The circuit is not completed
 Electricity always seeks the
shortest, fastest path to an area
of lower voltage.

This path, or circuit, would only
be completed if the bird was
touching something other than
the single wire.

Otherwise, the current stays on
its path through the line.
Larger Birds in Danger
 Larger birds sometimes
complete the circuit when
their wings touch another
line or the pole.
 Once the circuit is
completed, the electrical
current flows through the
bird to the area of lower
voltage, resulting in
electrocution.
Utility Worker Precautions
 Utility workers often work
near damaged lines or in
wet conditions where
electrocution is possible.
 To protect themselves they
use rubber gloves and
boots (rubber is a poor
conductor of electricity),
insulated tools, and rubber
mats and sheets to protect
against exposed wire.
Why is the ground prong longer than the flat prongs?
 So it will be first to be
plugged into a
socket…thus a ground
connection is established
just before the appliance
is electrically connected
You asked for it!
Why do the two flat prongs on plugs for most
electrical appliances have holes in them?
 If you unplug any appliance in your house, there is a 98 percent change




that the two flat prongs have holes in them.
There are three reasons for those holes.
First, if you were to take apart an outlet, and look at the contact wipers that
those prongs slide into, you would find that they have bumps on them.
These bumps fit into the holes, so that the outlet can grip the plugs prongs
more firmly. This prevents the plug from slipping out of the socket due to
the weight of the plug in the cord. It also improves the contact between the
plug and the outlet.
Second, electrical devices can be factory sealed, or locked out, by the
manufacturer or owner, using a plastic tie, or a small padlock that runs
through one or both of those prong holes. For example, a manufacturer
might apply a plastic band through the hole, and attach a tag to it that says
‘you must do blah, blah, blah, before plugging in this device’. The user
can’t plug in the device without removing the tag, so the user is sure to see
these instructions.
Third, there is also a small savings in raw materials for the manufacturer of
the actual plug prong. Every little bit helps.
TASER
 http://stunguns411.com/How-Dangerous-is-the-
Average-Stun-Gun-Volt.html