Many people are unsure about which aspect of electricity, voltage or current, poses the greater threat to human life. Voltage represents the electrical potential difference, acting as the “push” or pressure that drives electrical charge. Current, on the other hand, is the actual flow of electrical charge, measured in amperes. This article clarifies which factor is primarily responsible for harm during an electrical shock.
The Direct Answer: It’s the Current
Current, or amperage, causes injury and can be lethal during an electrical shock. While voltage is necessary to initiate and drive this current, the severity of the shock is determined by the amount of current that passes through the body. Even very small currents can be dangerous. For instance, an alternating current (AC) as low as 30 milliamperes (mA) passing through the chest for more than one second can induce ventricular fibrillation, a chaotic and ineffective heart rhythm. Direct current (DC) requires a slightly higher threshold, with 90 to 130 mA needed for the same effect.
How Electricity Harms the Body
Electrical current harms the human body through several mechanisms, primarily by interfering with its natural electrical signals and causing tissue damage. The human body relies on electrical impulses for nerve transmission and muscle control, including the heart’s rhythm. When an external current passes through the body, it can disrupt these delicate biological processes.
One of the most dangerous effects is ventricular fibrillation, where the heart’s electrical activity becomes disorganized, leading to ineffective pumping of blood. Currents between 100 and 300 milliamperes can cause this life-threatening condition.
Electrical shock can also lead to respiratory arrest by paralyzing the muscles that control breathing, particularly the diaphragm. This can occur if the current passes through the brain or causes prolonged muscle paralysis.
Electrical current also converts electrical energy into heat as it passes through resistive tissues, leading to internal and external burns. These electrical burns can be severe and may not always be apparent on the surface, often causing more extensive internal damage. Additionally, involuntary muscle contractions, or tetanic spasms, can occur due to electrical stimulation, preventing a person from letting go of an energized object and increasing the duration and severity of the shock.
The Interplay of Voltage and Resistance
While current directly causes harm, voltage plays a crucial role by providing the “push” necessary to overcome the body’s electrical resistance and drive that current. The amount of current that flows through the body is directly proportional to the voltage applied and inversely proportional to the body’s resistance.
The body’s resistance can vary significantly depending on several factors. Skin resistance is a major component; dry, intact skin offers substantial resistance, while wet or broken skin dramatically lowers it, allowing more current to flow at a given voltage. The path the current takes through the body is also critical; a current passing from one arm to the other, for instance, is far more dangerous as it is likely to traverse the heart. The duration of contact also influences the severity, as longer exposure allows more energy to be delivered.
High voltage is dangerous precisely because it can overcome even high skin resistance to drive a lethal current through the body. Even if the body’s resistance is high, a sufficiently high voltage can still force enough current to cause severe injury or death.
Prioritizing Electrical Safety
Understanding the dangers of electricity is important for preventing injuries.
Always assume that any electrical wire is energized and take appropriate precautions.
Use personal protective equipment (PPE), such as insulated gloves and tools, to provide a barrier against electrical flow.
Keep water away from electrical devices and outlets, as water significantly reduces electrical resistance and increases the risk of severe shock.
Regularly inspect electrical cords and outlets for damage, such as fraying or cracks, and replace them if necessary.
Avoid overloading electrical outlets to prevent overheating and potential fires.
Familiarize yourself with your home’s circuit breakers and Ground Fault Circuit Interrupters (GFCIs). Circuit breakers protect against overloads and short circuits by automatically shutting off power. GFCIs detect imbalances in current flow and quickly interrupt power to prevent electric shock, especially in areas near water sources.
In the event of an electrical shock, do not touch the person if they are still in contact with the electrical source. Instead, immediately turn off the power source if safe to do so, or use a non-conductive object to separate the person from the source, then call emergency services.