By dangerous rivers the amperage or intensity of the electric current, which is dangerous for humans, is understood here.

Dangerous amperages

For the consequences of a current accident the amperage and the frequency, which flow by the body of humans concerned, are crucial. The effect on the body takes place on the one hand due to the physiological effect on ion channels, on the other hand on the thermal effect of the river. With frequencies over 1 kHz above all the thermal effects (burns starting from 500 mA) are harmful.

• up to 0,5 mA and have no effects and damages are not noticeable to the consequence.
• from 2 to 10 mA are theoretically harmless. Since these amperages are however more or less felt as unpleasant, they know fright reactions and thus accidents (e.g. Fall) to the consequence have.
• starting from 10 mA (releasing border) it comes to first muscle cramping, which in one "sticking remain themselves at the river "express can. In the worst case cramping the chest musculature can lead to a breath paralysis.
• from 10 to 50 mA (dependent on the current flow duration) no organic damage normally results. It is to be counted however on muscle contractions and breath difficulties. With high amperage can occur forecourt flares and temporary heart stop.
• from 50 to 500 mA (dependent on the current flow duration) arises with high probability heart ventricular fibrillations. Besides arise heart stop, respiratory arrest and (internal) burns.
• starting from 500 mA heavy (internal) burns (necroses) are added, which lead evtl only days after the accident to death.

It can general be said that amperages can have already deadly consequences starting from 50 mA.

On the other hand dangerous rivers can flow off also from humans for the technology. The human body can achieve very high tensions (e.g. several 10000 V between fingertip and a reference object after going over a carpet) by electrostatic loading. Following electrostatic unloading (e.g. Fingertip unloading), can lead to rivers of up to several whereby the current flow duration lies however within the range of nanoseconds (see ESD simulation models).

All electrical devices deliver leakage currents when affecting to the user. The electrical standards indicate limit values for the deriving stream, that are the rivers, which flow in the normal operation and in the case of an error (for example an interruption of protective grounding). One differentiates between affecting Rome (the river over the grounded body flows during contact of equipment), leakage current (river when affecting, if protective grounding is interrupted) and patient leakage current. The limit values of most standards for the leakage current are about 3,5 mA. The deriving stream are measured by reproduction of the human body for example by 2000 ohms a resistance. Electrical devices, which are used as media, must be examined regularly. For this measuring instruments are often used, which measure the spare leakage current. This is a simplified procedure after VDE0710, which however in the TN-net with symetrischem structure Y indicates measured values double to condensers. Therefore the VDE0710 permits to halve the measured value.

Factors

The danger of the river depends on several factors:

Flow duration: The longer the river on the body works, the more strongly is also the effects. Thus already an amperage of 50 mA is sufficient, in order to cause a heart stop at one duration of some seconds, whereby at one duration of some milliseconds a much higher amperage is necessary for it.

Type of current: Alternating current is particularly more dangerous regarding heart ventricular fibrillations, about 3 time at longer flow duration, than direct current.

Further one: The range of the body surface, the kind of the contact and the condition of the current conduction place (humidity, temperature) and individual physiological characteristics of the affecting person represent likewise important factors.

Purchase for tension

The amperage depends directly on the electrical tension. Only if sufficient tension is present, a sufficiently strong river can flow. Against the household plug socket a tension of 230 V~ rests.

The amperage, which flows by humans, can after the Ohm's law,

I = \ frac {U} {R},

U = tension (volt)

R = resistance (ohm)

I = amperage (A)

is determined, whereby humans possess a resistance of approximately 1000 ohms (e.g. hand to hand, hand to foot).

Ex.: In the case of a tension of 230 V ohm, an amperage of 230 mA results after I = 230V/1000.

See also

• Electrical impact
• Dangerous tensions
• The five safety rules
• Electrical smog

Related links

• Effects of the electric current in the human body

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