An electrical injury occurs when a person contacts an electric current, potentially damaging skin or internal organs. There isn’t a single numerical answer to how many volts a human can withstand. Shock severity is influenced by factors beyond voltage, including current magnitude, its path through the body, and contact duration. Understanding these elements is essential for comprehending electricity’s true dangers.
Understanding Voltage and Current
Electricity involves two fundamental concepts: voltage and current. Voltage, also known as electric potential difference, represents the “pressure” or force that drives the flow of electrical charge through a circuit. It is measured in volts (V) and indicates the potential energy available to move electrons from one point to another. Current, on the other hand, is the actual flow of electric charge, measured in amperes (A).
Consider a water hose: voltage is like the pressure, and current is the flow rate. Higher voltage means more “pressure” for electrons. However, current, the actual flow of electrons through the body, primarily causes harm, not voltage alone.
Factors Determining Shock Severity
The danger of electrical shock depends on several variables, explaining why no single voltage can be “withstood.” Body resistance plays a significant role. Dry skin offers high resistance (up to 500,000 ohms), but wet or broken skin drastically reduces it (sometimes to 1,000 ohms), allowing more current to flow.
The current’s path through the body is another factor. Hand-to-hand flow often passes through the heart and lungs, significantly increasing injury risk. A path through the head can affect the nervous system. Prolonged exposure to current also increases damage, as it delivers more energy to the body.
The type of current (AC vs. DC) also influences shock severity. AC is generally more dangerous than DC at similar levels. AC (50-60 Hz) effectively disrupts the heart’s rhythm, leading to ventricular fibrillation.
AC also causes sustained muscle contractions, known as the “no-let-go” effect, which can prevent release and prolong exposure. In contrast, DC often causes a single, powerful muscle contraction that might throw a person away from the source, limiting contact time.
How Electrical Current Affects the Body
The human body can perceive even small electrical currents. The sensation threshold, the minimum current felt, can be as low as 1 milliampere (mA) for AC and 5 mA for DC. This sensation is described as a faint tingling.
As current increases, involuntary muscle contractions occur. Around 10 mA of AC, strong contractions can make it impossible to release the electrical object (the “let-go threshold”). This sustained contraction can lead to prolonged exposure and increased injury.
Higher currents, approximately 50 to 150 mA, can cause extreme pain and respiratory arrest by affecting the muscles responsible for breathing. Ventricular fibrillation, where the heart’s electrical activity becomes chaotic, preventing it from pumping blood, can occur with AC currents as low as 30 mA and DC currents of 90 to 130 mA if the current passes through the chest. If not treated quickly, ventricular fibrillation is fatal.
Electrical current can also cause severe burns, both external at the entry and exit points, and internal along the current’s path, due to the heat generated as electricity passes through tissues.
Electric shock can also damage the nervous system, leading to symptoms like pain, numbness, weakness, loss of coordination, memory issues, or seizures. This occurs as current disrupts nerve function and damages the myelin sheath that insulates neurons.