An electric shock occurs when a person becomes part of an electrical circuit, allowing current to flow through the body. While the voltage, measured in Volts, represents the electrical potential or driving force, it is the current, measured in Amperes or Amps, that directly determines the severity and outcome of the shock. The number of amps that pass through the body is the true metric for assessing danger and the likelihood of a fatal event. This measure of current flow is what causes the physiological damage, leading to muscle contractions, nerve disruption, and potentially heart failure.
Defining Voltage Current and Resistance in Shock
The interaction between the three core electrical variables—voltage, current, and resistance—is governed by Ohm’s Law. This fundamental relationship states that the current flowing through a conductor is directly proportional to the voltage applied across it and inversely proportional to the resistance it encounters. This can be expressed mathematically as I = V/R.
Voltage is the electrical potential difference that acts as the force pushing the charge, similar to water pressure in a pipe. Current is the actual flow of electrons, measured in amperes, and is the factor that causes injury by stimulating nerves and heating tissues. Resistance is the body’s opposition to this flow, which is measured in Ohms.
The body’s resistance is not a fixed quantity and is largely determined by the skin, which acts as the primary electrical barrier. Dry, intact skin can have a resistance of 100,000 Ohms or more, but wet skin dramatically lowers this value, sometimes to as little as 1,000 Ohms. High voltage is dangerous because it can overcome the skin’s resistance, permitting a much greater current to flow through the body’s internal, low-resistance tissues.
Specific Current Levels and Bodily Reactions
The question of “how many amps kill” is answered by looking at the specific thresholds of current, measured in thousandths of an ampere, or milliamperes (mA). The first threshold, perception, can occur at currents as low as 1 mA, which causes a faint tingling sensation. At about 5 mA, the shock is felt more distinctly but is generally not painful.
A more dangerous threshold is the “let-go” range, typically between 9 and 30 mA for men and 6 to 25 mA for women. Within this range, the electrical current causes involuntary muscle contractions that can make a person unable to release the energized object, prolonging the exposure. If the current flows for an extended duration, it can lead to respiratory paralysis when the current causes the muscles responsible for breathing, such as the diaphragm, to seize.
The most frequent cause of death from electrocution is ventricular fibrillation (V-Fib), which occurs at currents as low as 100 mA. V-Fib is a condition where the electrical signals that coordinate the heart’s pumping action become chaotic. The heart’s ventricles merely quiver, immediately stopping the circulation of blood.
Currents exceeding 2,000 mA (2 Amps) can cause immediate cardiac arrest by forcing the heart into a sustained contraction, along with severe burns and internal organ damage due to the intense heat generated.
How Electrical Pathway Influences Fatality
The path the electrical current takes through the body is highly significant in determining the severity of the shock. A current that passes through the chest is far more dangerous than one that travels, for example, from one finger to an adjacent finger. This is because a current path crossing the chest is likely to pass directly through or near the heart, increasing the probability of inducing ventricular fibrillation.
Shocks that travel from hand-to-hand or hand-to-foot contact are particularly hazardous because they place the heart within the electrical circuit. The duration of the contact also modifies the risk, as longer exposure allows even a relatively small current to cause sustained muscle tetanus or reach the point in the cardiac cycle most vulnerable to V-Fib.
External factors that reduce the body’s resistance, such as perspiration or wet conditions, easily increase the current flow for a given voltage, thereby raising the risk of a fatal outcome.