Find the current through a person and identify the likely...

Find the current through a person and identify the likely effect on her if she touches a $120-\mathrm{V}$ ac source: $(\mathrm{a})$ if she is standing on a rubber mat and offers a total resistance of $300 \mathrm{k} \Omega ;$ (b) if she is standing barefoot on wet grass and has a resistance of only $4000 \mathrm{k} \Omega$.

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Key Concepts

Ohm's Law

Ohm's law is a fundamental principle in electronics which states that the current through a conductor between two points is directly proportional to the voltage across the two points and inversely proportional to the resistance. This law (I = V/R) is essential for calculating the current that would flow through a body when exposed to a given voltage and provides the basic framework for analyzing the circuit.

Human Body Resistance

Human body resistance varies significantly due to factors such as skin condition, moisture, and the point of contact with the electrical source. It plays a critical role in determining how much current flows through an individual when they encounter voltage. On dry surfaces, the resistance tends to be higher, while in situations like wet conditions, resistance drops, leading to potentially more dangerous current levels.

Effects of Electrical Current on the Human Body

The physiological effects of electrical current depend on the magnitude and duration of the exposure. Even small currents can cause perceptible shocks, and as current increases, it can lead to muscle contractions, burns, or even fatal outcomes such as ventricular fibrillation. Understanding these thresholds is crucial in assessing the risks in electrical safety scenarios.

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