Electrical Maintenance

Posted on Feb 6, 2014

The equation is: Putting some values to this equation, if a circuit has a resistance of 25 ohms (O) and a potential of 125 volts, the current that is drawn in this circuit would be 5 amps. This basic circuit will give you some understanding for the next subject that we will discuss: electric shock. An important concern when working near electrical equipment is the effects

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of electrical shock on the human body. When we understand what these effects are, we can examine the other electrical hazards found on the job. Most people are aware that the principal danger from electricity is that of electrocution, but few really understand just how minute a quantity of electric energy is required for electrocution. Actually, the current drawn by a 7 -watt, 120-volt lamp passed from hand to hand or from hand to foot is enough to cause fatal electrocution. Just as it is current and not voltage that heats a wire, it is current that causes physiological damage. Different values of 60-hertz alternating current (AC) and their effects on an average human are listed in ```Table 1```. In short, any current of 15 mA or more may be fatal, those between 100 mA and 4 amperes are probably fatal due to heart failure, and those above 5 amperes may be fatal from severe burns. It is a fact, however, that shocks in this last current range are statistically less dangerous than those in the 100 mA to 4 amperes range. In view of the wide diversity of injuries derived from contact with electric energy, it is only logical that there must be minimum exposure to energized parts to prevent electric shock or electrocution. Ohm`s law may be used to determine the current, which is the value of interest, with the human body serving as the resistive element of the circuit. The E of Ohm`s law is the voltage of the system itself. The...

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