Electric shock is a physiological reaction that occurs when electric current passes through the human body. This phenomenon involves direct contact with an electrical source, causing damage to the skin or internal organs. This article explains how electricity interacts with the body and the factors that influence the severity of an electrical injury.
Basic Electrical Principles
Electrical concepts like voltage, current, and resistance are fundamental to understanding electric shock. Voltage represents the electrical potential difference, acting as the force that pushes electric charge through a conductor. This force drives the flow of electrons, known as electric current.
Current is the primary factor that causes physiological effects and injury in the human body. Resistance describes the opposition to the flow of electric current. The human body acts as a conductor, and its resistance, particularly that of the skin, plays a significant role in determining how much current will flow for a given voltage.
Current’s Path Through the Body
For an electric shock to occur, electricity must enter and exit the human body, completing an electrical circuit. The specific pathway the current takes through the body is a significant determinant of injury severity. Current passing through vital organs like the heart, brain, or lungs is particularly dangerous. For example, a current traveling from one hand to the other, or from an arm to a leg, is more likely to traverse the heart, increasing the risk of severe cardiac effects. Damage to the central nervous system can occur if the current passes through the head.
How Electricity Harms the Body
Electric current disrupts the body’s normal physiological functions through several mechanisms. It interferes with nerve impulses, which are electrical signals. This disruption can lead to involuntary muscle contractions, sometimes so severe that a person cannot release their grip from the electrical source, a phenomenon known as the “let-go” threshold. Muscle contractions can also cause respiratory arrest by paralyzing the muscles involved in breathing, such as the diaphragm.
Beyond muscle effects, electricity can induce dangerous cardiac arrhythmias, with ventricular fibrillation being a particularly life-threatening irregular heartbeat. This uncoordinated twitching of the heart’s ventricles can prevent effective blood pumping.
The body’s resistance to electric current also causes thermal burns, both external and internal. As current flows through tissues, it generates heat, leading to tissue destruction and coagulation. These burns can be much more extensive internally than what is visible on the skin surface.
Furthermore, electric current can cause direct cellular damage, disrupting cell membranes and leading to cell death.
Variables Determining Shock Severity
The severity of an electric shock is influenced by several interconnected factors. The amount of current flowing through the body is the most significant determinant; even small currents can be hazardous, with levels exceeding 30 milliamperes considered potentially fatal. Voltage drives the current, and higher voltages can lead to greater current flow and more severe injuries. However, low-voltage shocks can still be dangerous.
The duration of contact with the electrical source directly correlates with the extent of injury. Longer exposure allows more energy to be transferred to the body, increasing the likelihood of significant damage.
The path the current takes through the body is also critical; current passing through the chest, for instance, poses a higher risk to the heart and lungs. The body’s resistance, mainly due to the skin, also affects severity. Dry skin offers higher resistance, while wet or broken skin drastically reduces it, allowing more current to pass.
The type of current, whether alternating current (AC) or direct current (DC), also plays a role. AC is generally considered more dangerous than DC of the same voltage and current. This is because AC can cause sustained muscle contractions, preventing release and prolonging exposure. AC is also more likely to induce ventricular fibrillation.