Electricity and the Human Body

 Why 50 volts?

  • The typical body has a contact resistance of 500 ohms at the point of contact with the electrical source.
  • The body has an internal resistance of approximately 100 ohms.
  • Touch/Step potential to ground of about 5000 ohms (Ω is the symbol for ohms).
  • Combine the resistances to find the total resistance

  500Ω + 100Ω + 5000Ω = 5600 Ω

To find the amount of current the body is subjected to when in contact with 120V electrical source:

  • 50v / 5600 Ω = 8.9 mA
  • 120v / 5600 Ω = 21 mA
  • It is around 10 mA that the "cannot let go" level is reached. Once muscle lock-up occurs, exposure time is amplified and the probability of electrocution increases dramatically.


Figure 1: The Human Body is Conductive


Figure 2: Effects of Electric Shock on the Body