Transcript The Shocking Truth

The Shocking Truth
Electric Shock Science
What About You?
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Turn to a partner and tell of a time you
received an electric shock. If you know
the voltage involved, tell that
Measuring Body Resistance
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Hold the leads of a multimeter in both hands.
Make sure the meter is on the 2000k scale
(reads up to 2 million ohms)
The reading will be in thousands of ohms.
ie a reading of 673 means 673,000 ohms
Divide the reading into 120Volts
•
Example 120V/1,200,000  = 0.0001 A = 0.1ma
(record in your notes)
Repeat with wet hands
Shock Hazards
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1 ma (milliampere) can be felt
A few ma can be painful
More than 10 ma causes muscles to contract –
you may not be able to let go! And, you may
not be able to breathe and could die. Artificial
respiration could revive you.
Above 50-70 ma (AC) through the heart for
one second may cause heart muscles to
contract irregularly (ventricular fibrillation) and
not pump effectively. Fibrillation is very hard to
stop
Using a Defibrillator Could Get Your
Heart to Pump Properly Again
Strange But True
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Larger currents, around 1 Amp stop the
heart completely!
When the current stops, the heart
usually starts beating again
But larger currents also cause burns and
tissue damage, especially with voltages
around 500-1000 volts
Meet “Old Sparky”
Electric chair used
at Sing Sing prison
in New York
Up to 2450 volts AC
was used
Why AC is more deadly
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Human body acts as
if it had capacitance
in parallel with its
resistance
This provides an
additional path for
current to flow
Also AC is more
likely to cause
fibrillation
R
C
Common Causes of Shocks
faulty wiring, electrical
overloads, damaged
cords, sagging power
lines, exposure to
power lines, failure to
de-energize, lack of
warning or shielding
devices