Question

Find the current through a person and identify the likely effect on her if she touches a 120 V AC source in the following circumstances. (Note that currents above 10 mA lead to involuntary muscle contraction.)(a) Find the current (in mA) if she is standing on a rubber mat and offers a total resistance of 310 kΩ. (b) Find the current (in mA) if she is standing barefoot on wet grass and has a resistance of only 4100 Ω.

Answer 1

ANSWER:

(a) 0.387 mA

(b) 29.3 mA

STEP-BY-STEP EXPLANATION:

Given:

Voltage (V) = 120 V

(a)

Resistance = 310 kΩ = 310000 Ω

We calculate the current as follows:

$\begin{gathered} I=\frac{V}{R} \\ \\ \text{ We replacing:} \\ \\ I=\frac{120}{310000}=0.000387\text{ A}\cdot\frac{1000\text{ mA}}{1\text{ A}} \\ \\ I=0.387\text{ mA} \end{gathered}$

(b)

Resistance = 4100 Ω

We calculate the current as follows:

$\begin{gathered} I=\frac{V}{R} \\ \\ \text{ We replacing:} \\ \\ I=\frac{120}{4100}=0.0293\text{ A}\cdot\frac{1000\text{ mA}}{1\text{ A}} \\ \\ I=29.3\text{ mA} \end{gathered}$