Final answer:
It's not just the voltage but also the current that determines the danger of an electrical shock; the lethal danger lies in the combination of voltage, resistance, and subsequent current flow, which can result in conditions such as "ventricular fibrillation" or burns.
Step-by-step explanation:
The number of volts it takes to injure or kill a person cannot be stated definitively as it is the current that is the major factor in determining the severity of an electrical shock. However, because current (I) is related to voltage (V) and resistance (R) by the equation I = V/R, voltage is still a critical part of the equation. For instance, a person with dry skin might have a resistance of about 200 kΩ, and if they touch 120-V AC, roughly 0.6 mA of current would flow, which is usually harmless. But if the same person's skin is wet, reducing the resistance to 10 kΩ, the 120-V AC could produce a 12 mA current, which is above the "can't let go" threshold and can be dangerous. Currents between 100 and 300 mA can lead to "ventricular fibrillation," a potentially fatal disruption of heart rhythms, and at around 300 mA and above, the electric shock can cause burns.