Humans can conduct electricity because the human body contains ions and electrolytes that allow electric current to flow. However, the degree to which humans can conduct electricity depends on several factors. In this article, we will explore the basics of electricity conduction in the human body and examine the key factors that determine whether humans are good conductors of electricity or not.
How electricity flows through the human body
Electricity requires materials that contain free ions and electrons that can move and carry a charge. The human body contains such materials in the form of electrolytes and ions dissolved in water. Here’s a quick overview of how electricity flows through the human body:
– The main electrolytes in the body are sodium, potassium, calcium, and magnesium. These ions carry a positive or negative charge.
– Body fluids like blood and sweat contain these dissolved electrolytes and ions, making them conductive.
– When an external electric current is applied to the body, the charged ions and electrons flow towards the oppositely charged electrode. This flow of charges creates an electric current through the tissues and fluids.
– The current flows through the fluids, muscles, nerves, and organs since they contain mobile electrically charged particles.
– The skin offers some resistance but current can overcome it and travel through the various layers of the skin into the body’s interior.
So in summary, the electrolytes and dissolved ions in bodily fluids allow the human body to conduct electricity when an external electric field is applied. The body essentially acts like a complex circuit of conductive fluids, tissues, and pathways.
Key factors that determine electricity conduction
While the human body can conduct electricity, how good of a conductor it is depends on some key factors:
1. Body fluid and electrolyte levels
The electrolyte concentration in body fluids determines their conductivity. For example:
– Dehydration or water loss reduces the electrolyte content in the body, increasing resistance.
– Sweat contains electrolytes like sodium and chloride so sweating increases conductivity.
– Higher mineral content in the blood and tissues improves conductivity.
2. Callousness and dryness of skin
The skin acts as a resistor or insulator. However:
– Dry or calloused skin has a higher resistance.
– Wet skin or skin punctured by electrodes reduces resistance.
– Damaged skin like open wounds provides a direct current pathway inside the body.
3. Amount of muscle and fat
– Fat is an ineffective conductor. More body fat increases resistance to electric current.
– Muscle conducts electricity better than fat. Greater muscle mass reduces resistance.
– Overall, muscular individuals conduct better than people with high body fat.
4. Frequency of the current
– The human body offers greater impedance or resistance to higher frequency alternating currents.
– Lower frequency currents like 50-60 Hz can pass more easily compared to radio frequencies.
So in situations like electrocution accidents, the frequency of the power supply current matters.
5. Pathway of the current through the body
– The amount of current reaching the heart determines the risk of electrocution.
– If the current passes through the chest cavity, it can cause cardiac arrest and ventricular fibrillation.
– Pathways through the extremities are less dangerous.
6. Voltage and amplitude of the current
– The driving voltage determines how much current can enter the body.
– Higher the voltage, greater is the current flow through the body for the same resistance.
– Greater current flow causes more stimulation of muscles and nerves and increases risk of death.
How the human body compares to metal conductors
The human body is millions of times more resistive than metals like copper:
| Material | Resistivity (ohm-meter) |
|---|---|
| Silver | 1.6 x 10-8 |
| Copper | 1.7 x 10-8 |
| Gold | 2.4 x 10-8 |
| Aluminum | 2.7 x 10-8 |
| Tungsten | 5.6 x 10-8 |
| Steel | 1.0 x 10-7 |
| Human body | 1000 to 100,000 |
As seen above, metals like copper and gold have very low resistivity, allowing them to conduct electricity with great efficiency. The human body’s resistivity is nearly ten million times higher.
So in summary, the high ionic concentrations in the human body allow it to conduct electricity reasonably well compared to insulators like plastic or glass. But human tissues are far less conductive and much more resistant than metallic conductors.
Voltage and current flow in the human body
Let’s take a closer look at the relationship between voltage and current as electricity flows through the human body.
Ohm’s Law
According to Ohm’s law:
Current (I) = Voltage (V) / Resistance (R)
Where resistance is measured in ohms.
For the human body, a typical resistance value used is 1000 ohms from hand to hand for a dry unbroken skin.
Examples
Scenario 1) If we apply a voltage of 100 V across a dry hand, the resulting current flow is:
I = V/R
I = 100 V / 1000 ohms
I = 0.1 A or 100 mA
So we can see that a 100 V potential can create a current flow of 100 mA through the human body.
Scenario 2) Now if the skin is wet or broken, the resistance may drop to 500 ohms. Then the current flow for 100 V is:
I = 100 V / 500 ohms
I = 0.2 A or 200 mA
This shows how wet skin or damaged skin reduces body resistance, allowing more current to flow at the same voltage.
Effects of current flow in the human body
| Current | Effect |
|---|---|
| 1 mA | Barely perceptible |
| 5 mA | Slight shock felt |
| 10-25 mA | Painful shock |
| 50-150 mA | Extreme pain, muscle contraction |
| 200-500 mA | Damage to tissues and organs |
| > 500 mA | Ventricular fibrillation, heart failure, and death |
As the above table shows, currents above 50-100 mA can be extremely dangerous and even fatal.
Methods to measure body resistance
There are several techniques used to measure electrical resistance across the human body:
1. Direct current stimulation
– A small direct current is passed through two electrodes in contact with the body.
– The resulting voltage drop is measured.
– Then body resistance is calculated using Ohm’s law.
2. Resistance or impedance plethysmography
– Small amplitude alternating current is passed through body segments of interest.
– Changes in electrical impedance are used to calculate resistance.
– Allows tracking of blood flow and blood pressure cycles.
3. Bioelectrical impedance analysis (BIA)
– Alternating current is passed through the body and impedance measured.
– Since impedance is proportional to body water content, BIA can estimate body composition.
– Widely used to measure body fat percentage.
4. Electrical impedance tomography (EIT)
– Multiple small alternating currents are injected into the body.
– The resulting potentials are measured using electrode arrays.
– Advanced algorithms compute impedance distribution.
– Used to image impedance changes for medical diagnosis.
So in summary, these methods allow us to safely and accurately measure electrical conduction pathways and resistances across the human body.
Conclusion
While the human body can conduct electricity due to the presence of electrolytes, it is still millions of times more resistive than metallic conductors like copper. Factors like body fluids, skin condition, voltage levels, and current pathways determine how easily electricity flows through a person. Higher voltages or currents can be dangerous or lethal as they exceed the safe conduction limits of human tissues. Proper safety precautions are necessary to avoid electrocution when working with electrical sources. Advanced medical techniques allow measurement of the natural or induced electrical currents within the body.