The human body, while not typically thought of as an electrical component, possesses inherent electrical properties. Electrical signals are fundamental to many bodily functions, from nerve impulses to muscle contractions. The human body exhibits resistance to electricity. This resistance, however, is not static; it can fluctuate significantly based on various factors. Understanding how the body’s electrical resistance changes provides insight into its interaction with external electrical sources.
Understanding Electrical Resistance
Electrical resistance is a fundamental property in physics that describes the opposition a material offers to the flow of electrical current. It hinders the movement of electrons. This opposition arises from collisions between the moving electrons and the atoms within the conducting material, converting some electrical energy into heat.
The relationship between the electrical push, known as voltage, the flow of electricity, called current, and resistance is interconnected. When voltage is applied across a material, current attempts to flow. Resistance then determines how much current can pass through. If resistance increases while the voltage remains the same, the current will decrease, and conversely, if resistance decreases, more current will flow.
The Body’s Natural Resistance
The human body’s electrical resistance is largely attributed to its outermost layer, the skin. Dry skin, particularly the dead cells of the epidermis, acts as a significant protective barrier against electrical current. This dry layer, composed of dead cells, lacks free ions, making it a poor conductor with high electrical resistance. Dry skin can offer resistance ranging from 100,000 ohms to 500,000 ohms, and sometimes even up to 1,000,000 ohms.
In contrast to the skin, the internal tissues and organs of the body have a much lower electrical resistance. These internal components, rich in fluids and electrolytes like blood, are better conductors. The internal resistance of the human body, excluding the skin, can be as low as 300 to 1,000 ohms. The skin serves as the body’s primary defense, preventing current from reaching these more conductive internal structures.
How Wetness Changes Resistance
The presence of moisture on the skin dramatically alters the body’s electrical resistance. While pure water is a poor conductor of electricity, the water encountered in daily life, such as sweat or tap water, contains dissolved impurities like salts and minerals. These impurities break down into ions, charged particles that facilitate electrical current flow.
When the skin becomes wet, this conductive layer of water and dissolved ions forms on its surface. This moist film significantly reduces the high resistance offered by the dry outer layer of the skin. Water penetrates the skin’s outer layers, mixing with existing salts and connecting with sweat glands to enhance conductivity. This mechanism drastically lowers the skin’s resistance, allowing electricity to pass through more easily.
For instance, the resistance of wet skin can drop significantly, ranging from as low as 1,000 ohms to 150 ohms when fully immersed in water. This creates a direct, low-resistance pathway for electricity to enter the body, making it far more susceptible to electrical current.
Why Reduced Resistance Matters
The decrease in the body’s electrical resistance due to wetness has serious implications. If the voltage of an electrical source remains constant, a decrease in resistance will result in a significant increase in the amount of electrical current flowing through the body. This means that even a relatively low voltage, harmless with dry skin, can become dangerous if the skin is wet.
Increased electrical current can lead to various harmful effects. Currents around 1 milliampere cause a faint tingling, but at 10-20 milliamperes, sustained muscular contractions can occur, making it difficult to release an electrical source. Higher currents, particularly between 100 to 300 milliamperes, can disrupt the heart’s electrical patterns, leading to ventricular fibrillation, a severe cardiac event.
Elevated current levels can also cause severe burns, both external and internal, along the current’s path. The pathway current takes through the body is also important, with paths through the chest or head increasing the risk. Understanding how wetness reduces resistance emphasizes the importance of electrical safety, especially in damp environments or when handling electrical equipment with wet hands.