30 Sep What is electrical shock hazard
An electric shock can be defined as the feeling, sensation, physiological response or injury to the human body caused as a result of electricity or an electric current passing through it. This reaction takes place when the human body or part of the human body comes into contact with a power source or source of electricity and the current is substantial enough to pass through the skin, muscles, hair and the blood stream which has a lot of elements in it that conducts electricity and elements that do not conduct.
Negligible or small electric currents cannot be felt by the human body for any response. When the electric current increases in magnitude and becomes stronger, and passes through the human body, it sparks a response and the victim is electrically shocked and in the event, he/she as holding the power source that is energized, he/she may fail to release it owing to continued electrical shock.
Larger electric currents may result in heart problems such a fibrillation as well as damage to other body tissues. Electrocution occurs when death is the end result of electric shock.
Electric shock can also be the damaging exposure to electric current which travel through the nervous system of the human body and cause tissue and muscle damage in sections and patches. The end result of this is a complex regional pain syndrome anywhere on the body and is random depending on the magnitude of electricity and extent of the damage.
What determines the extent and severity of an electric shock
The extent to which an electric shock damages the human body and the severity of the physiological response is dependent on the current flowing through the human body a factor of the magnitude of electricity from the source. This is impacted by the electromotive force from the power source measure in volts and the contact resistance measured in ohms. The following formula is observed:
Current(I) = Electromotive Force(E)/Contact Resistance(R)
Electric Shock Values
- Electrical Sensation- tingle sensation occurs at about 0.25 to 0.5 mA for an adult female and between 0.50 and 1 mA for an adult male.
- Uncomfortable sensation- current over 1-2 mA is very uncomfortable to both sexes.
- Maximum ‘Let-Go’ Level- the maximum ‘Let-Go’ threshold level for a female is approximately -9 mA and for a male it is about -15 mA.
The ‘Let-Go’ threshold is defined as the current where the human body loses control of all the muscles and the electric current passing though the human is the one that causes the muscles to contract and relax. This continues until the electric current is no longer present.
Types of electric shocks
Electric shocks affecting the human body have two sources. This can be a direct contact source where the human body comes into contact with an exposed conductor or conductive part of an appliance or a circuit. This is where mitigated laws for insulation come in. The second is an indirect contact source which is prevented when an electrical system, circuit, appliance or equipment is properly earthed to offer an alternative path for electric current.