electrical shocks and safety

8/6/2019 Electrical Shocks and Safety

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� WHAT IS ELECTRICAL SHOCK?

� An electric shock occurs upon contact of a

human body with any source of voltage high

enough to cause sufficient current throughthe skin, muscles or hair.



� Electricity requires a complete path (circuit)

to continuously flow.

� The flow of electrons is necessarily brief when

static charges are equalized between twoobjects.



� Without two contact points on the body for

current to enter and exit, respectively, there

is no hazard of shock. This is why birds can safely rest on high-voltage power lines

without getting shocked: they make contact with the circuit at only one point.



�WHAT IS MINIMUM CURRENT?� The minimum current a human can feel : 1

milliampere (mA).

� The current may cause tissue damage or

fibrillation if it is sufficiently high.

� Generally, currents approaching 100 mA arelethal if they pass through sensitive portionsof the body.



�Shock effects� Burns� Heating due to resistance cause extensive and deep

burns.� Voltage levels of 500 to 1000 volts tend to cause internal

burns� Neurological effects� Current can cause interference with nervous control,

especially over the heart and lungs.� When the current path is through the head, it appearsthat, with sufficient current, loss of consciousness almost always occurs swif tly.

� Arc-flash hazards



� It is sometimes suggested that human

lethality is most common with alternating

current at 100250 volts; however, death hasoccurred below this range, with supplies as

low as 32 volts. Shocks above 2700 volts areof ten f atal, with those above 11000 volts

being usually f atal. Shocks with voltages over40,000 volts are almost invariably f atal.



� Ventricular Fibrillation� A domestic power supply voltage (110 or 230 V), 50 or 60-Hz AC current through the chest for a fraction of a secondmay induce ventricular fibrillation at currents as low as 60mA.With DC, 300 to 500 mA is required.

� If the current has a direct pathway to the heart (e.g., via a cardiac catheter or other kind of electrode), a much lowercurrent of less than 1 mA (AC or DC) can cause fibrillation.

� If not immediately treated by defibrillation, fibrillations

are usually lethal because all the heart muscle cells moveindependently instead of in the coordinated pulses neededto pump blood to maintain circulation. Above 200 mA,muscle contractions are so strong that the heart musclescannot move at all.



� The resistance of human skin varies from

person to person and fluctuates between

different times of day. In general, dry skin is a poor conductor that may have a resistance of

around 100,000 , while broken or wet skin may have a resistance of around 1,000 .



� Point of entry� Macroshock:Current across intact skin and

through the body.Current from arm to arm, or

between an arm and a foot, is likely to traversethe heart, therefore it is much more dangerousthan current between a leg and the ground. Thistype of shock by definition must pass into thebody through the skin.

� Microshock: Direct current path to the heart tissue, the shock is required to be administeredfrom inside the skin, i.e. a malfunctioning pacemaker, or ungrounded catheter etc.



�Deliberate uses� Medical uses: Electric shock is also used as a medical

therapy, under carefully controlled conditions:� Electroconvulsive therapy or ECT� As a treatment for fibrillation or irregular heart

rhythms: defibrillator and cardioversion.� As a method of pain relief : Transcutaneous Electrical

Nerve Stimulator� As an aversive punishment for conditioning of

mentally handicapped patients with severe behavioralissues.



� Law enf orcement and personal defence.

� Electroshock weapons are incapacitant

weapons� Torture.

� Capital punishment.



� FirstAid For Electric Shock � The victim usually gets stuck to the source of the

electricity, and it is important that you first separate

him from the electrical source.� Turn off the power supply switch and disconnect the

plug. It's best to simply turn off the main power supplyor pull out the fuse. Of ten, simply turning off theswitch may not stop the flow of electricity.

� In certain circumstances it may be quicker to simplypull the victim away from the electrical source.

� Do NOT touch the victim with your bare hands, or theelectric current will pass through you as well.



� If you are barefoot, stand of some clothes or any handnon-conductive material like wood or paper.Make sureyou are not standing on anything that is wet.

� Throw a blanket over the victim and try to separate himfrom the source. Make sure you don't touch him though.You can also use dry, nonconductive material such as a wooden broom handle or a chair to separate the victimfrom the live current

� Once the victim is separated, check to see if he is

breathing. If breathing has stopped or seems slow,administer articificial respiration immediately.� Let his head be slightly lower than the rest of the body,

and raise his legs.� Cover the victim with a blanket.



� Move the victim as little as possible.He mayhave suffered in juries to his spine and neck.

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f the victim has a burn, remove the clothing from the burned area (unless it's stuck to theskin) and rinse it in cool, running water.Coverthe burn with a dressing.

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Don't apply ice or any other ointment orcotton dressing to the burn.� Call for emergency medical attention as soon

as possible



� PRECAUTION� Check for frayed or cracked electrical cords, and

replace them.� Make sure that outlets and extension cords are not

overloaded. Either change the cord to a higher ratedone or unplug some of the appliances.

� Check to see that all lamps and light fixtures areoutfitted with bulbs of the correct wattage; this will

prevent overheating which could lead to a fire.� Make sure that all fuses are the correct size for the

circuit. The wrong size fuse can create a serious firehazard.



� If an appliance has repeatedly blown a fuse,tripped a circuit breaker, or shocked you, unplug it and have it repaired or replaced.

� If an outlet or switch is unusually warm or hot tothe touch, an unsafe wiring condition couldexist.Have it checked by an electrician as soon as possible.

� Always follow the manuf acturer's instructionsand safety precautions for all home appliances.

� Have earthing installed in your house.

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