We all feel electrical shocks. Which is really responsible for the shock, voltage or current?

The ultimate cause is the amount of electricity flow in the body, so it can be said to be current.

However, there are other factors, one of which is voltage, to consider:

1) Path of flow: If the internal organs are in the path of current flow, much smaller currents can cause a fatality.

Hence, if the shock is applied between one arm and the other arm, such as when holding Live wire in one hand and Neutral in the other, the current can pass through the heart, causing death. The same source of electricity may perhaps not be fatal if the points of the shock delivery are an arm and a leg, for example.

This is probably also the reason that execution by electrocution is done by placing the electrodes across the head. So that the current path is through the brain.

2) Resistance of the body: This is the resistance offered by the human body to electric flow. This can vary depending on moisture level. It can also vary with voltage as mentioned in the next point.

3) Voltage: Important to note that the resistance of the body changes according to voltage applied! Hence, it is not just a simple linear increase of current with voltage (in accordance with ohm's law).

The skin is an insulator, and contributes greatly to the high resistance of the body (order of Mega-ohms) for low voltages. However, at high voltages, dielectric breakdown of skin occurs which drastically reduces resistance of body by almost 1000 times!

This is what makes voltages above a certain level fatal, since it can cause current flow to increase drastically.

4) Duration of shock: In general, higher the duration of shock - greater the damage.

As an interesting example, consider static electricity. We can easily build up static potentials in excess of 10000 Volts, which is enough to break down air at short distances! However, we don't see any deaths caused by handshakes. :)

This is because, while the potential generated by static can be huge, the total amount of source charge available is really small. So the duration of the current flow is also too small to have any effect.

So to answer the question, while it is the flow of electrons (current) that causes us problems, there are other factors (including voltage) which can significantly affect how much of this electron flow occurs.