# Electrical injuries

Electrical injuries (also called electric shocks) are injuries of human beings or animals caused by electric current passing through the human or animal body. Depending on several factors such as amplitude of current, duration of current flow and current path (e.g., right hand to both feet), different effects may occur in the body: faint tingling, involuntary muscle contractions, burns, cardiac arrhythmia as well as electrocution. In the following the focus is on the effects on humans.

## Definitions

Electric current is the directed flow of free charge carriers (e.g., electrons or ions); this means the transmission of electrical energy. Current [I] is measured in amperes [A]. Voltage is the difference in electrical potential energy between two points and is measured in volts [V]. The electrical resistance is a measure of how much an electrical conductor opposes the current flow. The unit of the electrical resistance is Ohm [Ω].

The relationship between electric current, voltage and resistance is given by Ohm’s law:

I = U/R

This means, the higher the voltage and the smaller the resistance, the higher the current.

There are two types of electrical current: direct current and alternating current (see figure). Direct current (DC) is the unidirectional flow of electric charge (see left side/top of the figure). Alternating current (AC) occurs when the flow of electric charge periodically reverses direction (see right side/bottom of the figure). The frequency tells us how often this change happens per second. The unit of frequency is Hertz [Hz]. For example, an alternating current of 50 Hz has 50 periods per second. 