Electric shock

electric shock

1. ELECTRIC SHOCK
12/03/16

2. Student Name:Jariwala Harekrishna H.
Department: Civil (A)
Pen No:150430106037
Guided By:Tejas G. Misrty.
12/03/16

3. Contents:
How shock occurs
Preventing electric hazards
Ohm’s law of electricity
Effects of electrical shock on human body
How it happens

4. How Shock Occurs
•The severity of the shock received when a person becomes a part of an
electric circuit is affected by three primary factors:
•The amount of current flowing through the body
•The path of the current through the body
•The length of time the body is in the circuit.

5. Other factors that may affect the severity
Of shock are the:
•
Frequency of the current;
•
Phase of the heart cycle when shock occurs
•
General health of the person.

6. •
A difference of less than 100 mA exists between a current that is
barely perceptible and
one that can kill.
•
Muscular contraction caused by stimulation may not allow the victim
to free himself or herself from the circuit, and the increased duration
of exposure increases the dangers to the shock victim.
•
For example, a current of 100 mA for 3 seconds is equivalent to a
current of 900 mA applied for0.03 seconds in causing ventricular
fibrillation.
•
LOW VOLTAGE DOES NOT IMPLY LOW HAZARD

7. •
A severe shock can cause considerably more damage to the body than is
visible.
•
For example, a person may suffer internal
hemorrhages and destruction of tissues, nerves, and muscles.
•
In addition, shock is often only the beginning in a chain of events.
•
The final injury may well be from a fall, cuts, burns, or broken bones.

8. How Electricity Hurts PeopleHow Electricity Hurts People
Current Impact on People
1 mA no sensation
1-3 mA sensation, no pain
3-15 mA pain, most people can get away
15-30 mA pain, half of people freeze
30-75 mA pain, breathing difficult, asphyxiation
75-200 mA possible ventricular fibrillation
200-300 mA certain ventricular fibrillation
300+ mA severe burns, heart stops
CurrentCurrent Impact on PeopleImpact on People
1 mA 1 mA no sensationno sensation
11--3 mA 3 mA sensation, no painsensation, no pain
33--15 mA15 mA pain, most people can get awaypain, most people can get away
1515--30 mA30 mA pain, half of people freezepain, half of people freeze
3030--75 mA75 mA pain, breathing difficult, asphyxiationpain, breathing difficult, asphyxiation
7575--200 mA200 mA possible ventricular fibrillationpossible ventricular fibrillation
200200--300 mA300 mA certain ventricular fibrillationcertain ventricular fibrillation
300+ mA300+ mA severe burns, heart stopssevere burns, heart stops

9. Preventing Electrical Hazards
•Electrical accidents appear to be caused by a combination of three possible
factors:
unsafe equipment and/or installation; workplaces made unsafe by the
environment; and unsafe work practices.
•There are various ways of protecting people from the hazards caused by
electricity.
•These include: insulation; guarding; grounding; electrical protective devices;
and safe work
practices.

10. Voltage is almost always a constant so
electrical current levels are determined
by the resistance to flow. When there
is a potential for electrical shock we
can protect ourselves by maximizing
our resistance to current flow. This is
done by wearing insulating shoes and
gloves, and by not making direct
contact with a source of ground
potential such as plumbing or other
sources of ground.
V = I R
V = electrical potential (volts)
I = electrical current (amps)
R = resistance (ohms)
Ohm’s Law of Electricity

11. Our skin provides us with a natural barrier or resistance of approximately
1,000 to 100,000 ohms depending on several factors including skin
thickness and surface moisture.

12. Lower levels of AC than DC will produce painful shocks in humans while lower
levels of DC than AC can lead to fibrillation of the heart muscle. Women are
more sensitive to the effects of both AC and DC than are men.
Effects of Electrical Shock on the Human Body
Direct Current Alternating
MenWomen MenWomen
Perception Threshold 5.23.5 1.10.7
Painful Shock 0.5% 62 41 9.06.0
Painful Shock 99.5% 90 60 23 15
Ventricular Fibrillation500500 675675
All Units are in milliamps

13. Extension cords are approved for temporary use only. If extended use is required,
hard wiring such as a new outlet should be installed. Extension cords are easily
frayed, a condition which may expose bare wires. If not properly placed,
extension cords may also become a trip hazard.
Extension Cord Hazards

14. Power cords are doubly insulated and should be replaced if the outer layer of
insulation becomes frayed exposing wires.
Common Power Cord Problems
Exposed
Wires

15. Electrical Shock HazardsElectrical Shock Hazards
DonDon’’t use equipment with t use equipment with
damaged insulationdamaged insulation

16. Shorts cause a great increase in
the flow of current through the
cord producing heat and perhaps
initiating a fire.
Overloads occur when more
current flows through a cord than
it is rated to handle. Power strips
can be overloaded if too many
high current draw devices are
plugged in at one time.
A
B
C
D
Outlet or
Power
Strip
Plug
S
h
o
r
t
N
o
r
m
a
l
V = IR As
resistance decreases, current
increases.
Short circuit
Overloaded circuit

17. Another common way in which power cords can be overloaded is by plugging one
power strip into another. All of the current drawn by any device plugged into any of
the strips must flow through a single cord
Overloaded Circuit

18. Eyewashes should be located away from electrical devices and outlets. Outlets
within six feet of a sink or other source of plumbing must be GFCI protected in
order to minimize shock hazards. An unprotected outlet (non-GFCI) is illustrated
above.
Outlet without GFCI
Water and Electricity

19. A GFCI or ground fault circuit interrupter shuts off the flow of current upon
sensing a fault condition such as an electrical shock. Switches quickly open in
the GFCI device in order to prevent the shock victim from receiving a lethal
amount of electricity.
Switches
Hot Line In
Neutral Line In
GFCI
Receptacle
Current
Sensor
Function of a Typical GFCI
Load

21. •A (GFCI) is an electrical device which protects personnel by detecting
potentially hazardous ground faults and quickly disconnecting power
from the circuit.
•Any current over 8 mA is considered potentially dangerous depending
on the path the current takes, the amount of time exposed to the shock,
and the physical condition of the person receiving the shock.
•A GFCI compares the amount of current in the ungrounded (hot)
conductor with the amount of current in the neutral conductor.
•If the current in the neutral conductor becomes less than the current in
the hot conductor, a ground fault condition exists.
•The amount of current that is missing is returned to the source by some
path other than the intended path (fault current).
•A fault current as low as 4 mA to 6 mA activates the GFCI and
interrupts the circuit.
•Once activated, the fault condition is cleared and the GFCI manually
resets before power may be restored to the circuit
   

22. Approved Treatment for Physical Shock Patients
1)Keep patient lying down
2)Keep airway open
3)Elevate patients’ legs if no bones are broken
4)Keep patient warm if conditions are cool or damp
5)Give fluids if patient is able to swallow
6)Never give alcohol to patient
7)REASSURE the patient

23. Dry chemical extinguishers
(also know as ABC
extinguishers) are approved for
fighting electrical fires. The
label indicates the type of
extinguisher that is present.
Electrical fires should only be
fought if the situation is well in
hand. If you feel
uncomfortable fighting a fire,
pull the alarm and exit the
building.
Small
Nozzle
Test tag
should be
current
ABC
indicated
on label
Electrical Fires

24. Preventing Electrical Hazards
These include:
•Insulation
•Guarding
•Grounding
•Electrical protective devices
•
Safe work practices.

25. Stay clear of bare wires.Stay clear of bare wires.
Use GFCIs, they save lives!Use GFCIs, they save lives!
Never retouch anything that Never retouch anything that
has given you a shock.has given you a shock.
Protect cord insulation.Protect cord insulation.
Stay clear of power lines.Stay clear of power lines.
In Summary...In Summary...

26. T
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Made by:Jariwala Harekrishna H.
Guided by:Tejas G. Misrty.