Electricity through the body, II. The average bulk...

Electricity through the body, II. The average bulk resistivity of the human body (apart from surface resistance of the skin) is about 5.0$\Omega \cdot \mathrm{m} .$ The conducting path between the hands can be represented approximately as a cylinder 1.6 $\mathrm{m}$ long and 0.10 $\mathrm{m}$ in diameter. The skin resistance can be made negligible by soaking the hands in salt water. (a) What is the resistance between the hands if the skin resistance is negligible? (b) What potential difference between the hands is needed for a lethal shock current of 100 $\mathrm{mA}$ ? (Note that your result shows that small potential differences produce dangerous currents when the skin is damp.) (c) With the current in part (b), what power is dissipated in the body?

Electricity through the body, II. The average bulk resistivity of the human body (apart from surface resistance of the skin) is about 5.0$\Omega \cdot \mathrm{m} .$ The conducting path between the hands can be represented approximately as a cylinder 1.6 $\mathrm{m}$ long and 0.10 $\mathrm{m}$ in diameter. The skin resistance can be made negligible by soaking the hands in salt water. (a) What is the resistance between the hands if the skin resistance is negligible? (b) What potential difference between the hands is needed for a lethal shock current of 100 $\mathrm{mA}$ ? (Note that your result
shows that small potential differences produce dangerous currents when the skin is damp.) (c) With the current in part (b), what power is dissipated in the body?

Key Concepts

Bioelectrical Safety

Bioelectrical safety involves understanding the impact of electrical current on the human body, including recognizing thresholds where currents become dangerous or lethal. Factors such as skin resistance, the conductivity of body tissues, and the geometry of the current path are key in determining the risk associated with electrical shocks.

Ohm's Law

Ohm's Law is a fundamental principle that relates the voltage across a conductor to the current flowing through it and its resistance, expressed as V = IR. This law is essential for determining the necessary voltage to achieve a given current through any resistive element.

Electrical Power Dissipation

Electrical power dissipation in a resistor is the process by which electrical energy is converted into heat, calculated using the formula P = I²R. Understanding power dissipation is important in assessing the thermal effects and potential hazards in electrical systems.

Resistivity

Resistivity is a material property that quantifies how strongly the material opposes the flow of electric current. It is an intrinsic property that indicates the resistance per unit length and cross-sectional area of a material, and it is critical in calculating the resistance of any object made of that material.

Conductor Geometry

The geometry of a conductor, including its length and cross-sectional area, directly influences its electrical resistance. A longer conductor provides a longer path for the current and therefore higher resistance, while a larger cross-sectional area offers more pathways for charge flow, reducing resistance.

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