Contact currents
Stories from Physics
for 11-14
14-16
When someone stands close to a power line or a substation, the alternating fields present can induce currents in their body. A person standing directly below a transmission line may have currents of around 1 nA induced in the periphery of their body by the 60 Hz magnetic field.
When they touch a grounded conductor, such as a car, the person might experience a shock – an effect known as a contact current. Well-grounded individuals who touch large objects under power lines will draw the largest contact currents. Generally, contact currents are imperceptible, but, under the right circumstances, can be annoying or even painful.
References
U.S. Congress, Office of Technology Assessment, Biological Effects of Power Frequency Electric & Magnetic Fields—Background Paper, OTA-BP-E-53, Washington, DC: U.S. Government Printing Office, May 1989, p. 18
