7.3. Hazards of Electricity
| Shock | most common, can cause electrocution or muscle contraction leading to secondary injury which includes falls |
| Fire | enough heat or sparks can ignite combustible materials |
| Explosions | electrical spark can ignite vapors in the air |
| Arc Flash | can cause burns |
| Arc Blast | a pressure wave caused by expansion of copper in short circuit |
Fundamentals of Electricity
– Electrical current is the flow of electrons through a conductor.
– A conductor is a material that allows electrons to flow through it.
– An insulator resists the flow of electrons.
– Resistance opposes electron flow.
– Current Flows in a Loop or Circuit
Circuits are AC (alternating current) or DC (direct current). Usually, current is alternating current (AC). AC current has five parts:
– Electrical source
– HOT wire to the tool
– The tool itself
– NEUTRAL wire returns electricity from the tool
– GROUND
Electric Shocks. Current travels in closed circuits through conductors, example: water, metal, the human body. Shock occurs when the body becomes a part of the circuit where current enters at one point and leaves at another.
Severity of the shock depends on:
– amount of current
– determined by voltage and resistance to flow
– individual differences
Effects of Current Flow
| More than 3 milliamps (ma) | painful shock |
| More than 10 ma | muscle contraction |
| More than 20 ma | considered severe shock |
| More than 30 ma | lung paralysis – usually temporary |
| More than 50 ma | possible ventricular fibrillation (usually fatal) |
| 100 ma to 4 amps | certain ventricular fibrillation (fatal) |
| Over 4 amps | heart paralysis; severe burns |