Electric Current
Electricity and Magnetism

Telephone-induced lightning injuries

Stories from Physics for 11-14 14-16 IOP RESOURCES

Towards the end of the 1980s, in Australia, a survey reported that around 60 people a year were injured as a result of using landline telephones during thunderstorms. A 1998 report from the UK describes the case of a nine-year-old boy who used a landline during a thunderstorm: the phone was blown off the wall and the boy lost consciousness, suffered superficial burns and later developed a cataract.

Lightning strikes can cause current surges of between 3 and 5 kA in telephone lines, either by a direct strike or by induction from surges in power lines that run close to phone cables. When lightning strikes, the local Earth potential may increase. As telephones are held at a zero of potential relative to a remote Earth, the potential difference caused by a rise in local Earth potential can cause a current to flow, causing telephone users to experience a shock.

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