Answer
Put a 9000 ohm resistor in series with the body, then apply the voltage.
Work Step by Step
We should use a voltage divider circuit, as discussed in Example 19-3b (see Figure 19-6b).
Find the desired current to pass through the body, using Ohm’s law.
$$I=\frac{0.25V}{1800\Omega}=1.389\times10^{-4}A$$
Use this current and find the resistor that you should put in series with the body.
$$V_{battery}=I(R_{body}+R_{series})$$
$$R_{series}=\frac{V_{battery}}{I}-R_{body}=\frac{1.5V}{1.389\times10^{-4}A}-1800\Omega=9.0\times10^3\Omega$$