An electric shock occurs when electrical current passes through the body, causing a physiological effect. This happens when a person becomes part of an electrical circuit, allowing current to flow through their tissues.
Understanding Electrical Flow
Electricity involves the movement of charged particles. Understanding how it affects the body requires considering three basic concepts: voltage, current, and resistance. Voltage represents the “pressure” that pushes electrical charges through a circuit, similar to water pressure in a hose. Current is the flow of these charges, measured in amperes (amps), comparable to the volume of water flowing through the hose. Resistance is the opposition to this flow, measured in ohms, akin to how narrow a hose might be.
The human body, largely composed of water and electrolytes, conducts electricity. For a shock to occur, a complete circuit must form, allowing current to enter the body at one point and exit at another. If a person touches a live electrical source while connected to the ground or another conductive path, their body completes the circuit. The amount of current that flows depends on the applied voltage and the body’s resistance, following Ohm’s Law.
How Electricity Affects the Body
When electrical current passes through the body, it interferes with natural electrical signals essential for nerve and muscle function. Nerves transmit signals using small electrical impulses, and an external current can disrupt these communications. This interference can lead to involuntary muscle contractions, causing pain and spasms. These contractions can be severe enough to prevent a person from releasing the electrical source, known as the “let-go threshold,” prolonging exposure.
Electricity can also significantly impact the heart and respiratory system. The heart relies on precise electrical signals to maintain its rhythmic pumping action. An external current can disrupt these signals, leading to an irregular heartbeat (arrhythmia) or, more dangerously, ventricular fibrillation, where the heart flutters ineffectively. This can stop blood circulation and lead to cardiac arrest. High currents can also cause direct tissue damage through heat generation, resulting in severe burns both externally at contact points and internally along the current’s path.
What Determines Shock Severity
Several factors influence the severity of an electric shock. The magnitude of current flowing through the body is the most significant determinant of injury. Even low voltages can be dangerous if they drive enough current. For example, currents as low as 10 milliamperes (mA) can cause painful muscle contractions and loss of muscle control, while currents exceeding 75 mA can induce ventricular fibrillation.
The current’s path through the body also plays a role in shock severity. Current passing through vital organs like the heart or lungs, such as from hand to hand across the chest, is far more dangerous than current flowing through an extremity. The duration of contact with the electrical source directly correlates with injury; longer exposure increases the potential for harm, including burns and cardiac arrest.
Skin resistance primarily determines the amount of current that flows for a given voltage. Dry, calloused skin offers higher resistance, potentially up to 100,000 ohms, reducing current flow. Wet or broken skin significantly lowers resistance, sometimes to as little as 1,000 ohms, allowing greater current to pass through the body and increasing the risk of severe injury. Higher voltages can also break down the skin’s resistance, further increasing current flow.
Different Types of Shocks
Electric shocks originate from various sources, leading to different sensations and potential harms. Static electricity shocks, commonly experienced when touching a doorknob after walking across a carpet, involve a brief discharge of accumulated electrical charge. These shocks typically involve very high voltage (thousands of volts) but extremely low current, lasting only microseconds. The sensation is usually a quick, startling zap, and while uncomfortable, it is generally harmless due to minimal energy transfer.
Shocks from household current, such as those from an electrical outlet or faulty appliance, involve lower voltages (e.g., 110-240 volts) but deliver a sustained, higher current. This continuous flow can cause muscle spasms, pain, and, if sufficient current passes through the body, disrupt the heart’s rhythm or cause severe burns. Unlike static shocks, which dissipate almost instantly, household current continues to flow as long as contact is maintained, posing a more serious and potentially fatal threat.