From how many volts is an electric shock lethal?

You have probably already had electricity in some subject (physics for example) and heard of resistance, voltage and current. The “interplay” of those three and whether the flow is mono or biphasic plays a part in the danger.

It may sound strange, but the volts (the voltage) won’t kill you. A meadow wire, for example, can give a shock of 60,000 Volts. It would be an economic disaster if every horse or cow were ‘beaten to death’ by tapping its nose against the fence.

So… a taser gun isn’t deadly, but it will ‘knock’ you out with a force that is 30 times greater than the blow you feel from a pasture that grabs you.

The deadliest thing about electricity is the intensity I, the current (the Amperage, measured in A or mA). That is why the domestic 220V is deadly, because there is also current present. The house current is also protected by leakage current detectors: 30 mA for the bathroom and 300 mA for the rest of the circuit. This means that if the fuse box detects a leakage current of 30 mA on a circuit that may involve water (bathroom/hair dryer) the current will automatically drop. This is to avoid fatal accidents!

This will give you 2 indicators: low amps (30mA) are lethal to humans + if the skin resistance is reduced by a conductor then it becomes all the more dangerous (current jumps at 30mA on potential wet circuits and 300mA on dry ones) . That’s because humans are semiconductors, where the skin is resistant, but pores, blood, and nerves are not. Hard pressure (squeezing in a cramp), moisture or salts in the sweat reduces resistance and increases the intensity of current – even if the voltage remains unchanged (U=RI; P=R.I²; P=UI).

To give you an idea, when people are cardiac paced (pacemaker), the heart already follows currents of around 1 mA. That is in ideal circumstances with a ‘harpoon’ in the heart muscle itself (so very low resistance). On the other hand, if a person is defibrillated, it is with devices that can generate up to 70 A (= equivalent of 7 washing machines linked together). That is, the heart has a vulnerable and fairly invulnerable phase. However, they are so short and per heartbeat that you as a ‘layman’ can do nothing with them to protect yourself. However, a synchronous cardioverter will always shock in the depolarization phase (contraction) of the heart, never when it repolarizes. If this is done (asynchronously), the patient can immediately go into ventricular fibrillation (= sudden death).

10 mA at the “wrong moment” of the cardiac cycle (= 1 beat) can always be lethal. Alternating current is more dangerous because it changes phase and this about 50 x per second. This means that the current hits the heart at about 50x/s with 10 mA and the chance is much greater to hit the vulnerable phase of 1 cycle. That is not the case with direct current: there you only have the trick of ‘setting up’.

So: the combination of zero intensity, direct current and skin resistance does not make a taser gun a deadly weapon. Add current and it becomes a lightning strike: you know that many do not survive.

Goodbye,

Dirk Danschieter