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Devices (TV, Refrigerator, etc) are rated for maximum
power/voltage/etc. (They stop working if exceeded)
Devices can be overpowered by accident by
 overloading outlets – draws too much current
Example:

plugging too many things into the same outlet
Ground Fault (short circuit) – contact is made
between live and ground conductors

Example: Working hair dryer in water – plumbing is
connected to ground
Preventing Accidental Overload

Fuses



Circuit breakers




small filaments (like light bulbs)
Burn out when too much current is drawn
bimetallic strip heats up when too much current is drawn
bends when heated which opens switch to prevent current flow
http://electronics.howstuffworks.com/circuit-breaker2.htm
GFCI outlets and breakers



Complex circuitry that senses too much current almost
instantly
Opens circuit at outlet or breaker
http://home.howstuffworks.com/question117.htm
0.00l A and higher – feel shock
0.01A and higher – unable to release
0.02 A and higher – paralyzes respiratory muscles
(you can’t breath)
0.1 A and higher – ventricular fibrillation (erratic
heartbeat)
1.0 A and higher – “cooked”
Skin has very high resistance
– approximately 100,000 Ω
So, V = IR
10 V = I (100,000 Ω)
I = 0.0001 A
Remember! You can’t have a current without a
voltage