Physiological Effects
Electrical current does the damage. Currents less than 500 microamperes produce no sensation
or feeling. Sensory nerves are stimulated at current levels of 500 microamperes to 2 milliamperes.
Above 2 milliamperes, the motor nerves are stimulated, and muscles contract.
Above 1 ampere, burns are likely as a result of the power losses and heat generation in tissue.
Electrical sensitivity is a function of frequency. The frequency to which humans and
other biological systems are most sensitive lies in the range of 50 to 60 Hertz. At frequencies
above and below this range, more current is required before any sensation is felt,
and more current is required to stop the heart from beating.
Most injuries from electric shock are trauma injuries or burns. The trauma results from
the “startle reaction” or sudden muscle contractions. For an electrical shock to occur,
three conditions must be met: (1) there must be a difference of potential; (2) there must
be a path for current flow; and (3) sufficient current must flow.