Answer
See answers.
Work Step by Step
a. Use equation 19–7a to solve for the unknown resistance in the cardiac defibrillator.
$$V_C=\epsilon(1-e^{-t/RC})$$
We are told that the ratio $V_C/\epsilon = 0.95$.
$$0.95=1-e^{-t/RC} $$
$$0.05= e^{-t/RC}$$
$$ln(0.05)=-t/RC$$
$$R=\frac{-t}{Cln(0.05)}= \frac{-2.0s}{(1.0\times10^{-6}F)ln(0.05)}=6.7\times10^5\Omega$$
b. As specified in Section 19-7, the resistance between 2 moistened points on the human body is about $1000\Omega$. Use this value of the body’s resistance, and equation 19-7c, to find the capacitance of the human body.
$$\tau=RC$$
$$C=\frac{\tau}{R}=\frac{0.010s}{1000\Omega}=10\times 10^{-6}F$$
