Parameters for effects of electric current

The effects of electric current depend on the following parameters:

• Type of current (e.g., alternating current (AC) or direct current (DC)). Alternating current is more hazardous (especially in the low voltage range) than direct current as the ‘freeze’ (see Mechanisms of action) caused by alternating current can occur by repeated contraction of the muscles. In contrast, direct current induces only one muscle contraction which usually throws the subject away from the power source.
• Amplitude of current
• Voltage (e.g. low voltage, high voltage). Low voltage does not mean a lower hazard because in high-voltage electric injuries the subject is often thrown away from the source e.g. a power line and thus the current flow is interrupted. In low-voltage electric injuries, the no-let-go phenomenon can lead to a longer contact time resulting in more severe injuries. If skin breakdown occurs and thereby skin resistance is lost, the body resistance is minimized and a higher current flows through the body.
• Duration of current flow
• Human body resistance

The body resistance (also called body impedance) depends again on the following factors:

• Current path in the body, that is, how the current flows through the body and at which points the current enters and exits the body (e.g. right hand – left hand, right hand – both feet, right hand – thorax). The current path determines which tissues or organs are inflicted by the current.
• Touch voltage, i.e. the voltage between conductive parts when touched simultaneously by a person.
• Duration of current flow
• Current frequency
• Skin moisture (e.g., dry, wet, sweaty)
• Size of contact area (e.g., fingertip, palm of the hand)
• Exerted pressure