Answer
a. There is infinite resistance
b. 96$\Omega$
Work Step by Step
Use equation 18–6b to calculate the power.
$$P=\frac{V^2}{R}$$
a. When everything is unplugged, the power is zero. Zero power and zero current correspond to an infinite resistance. This makes sense because your house is basically an “open circuit”.
b. Use equation 18–6b to calculate the power, and solve for the resistance R.
$$P=\frac{V^2}{R}$$
$$R=\frac{V^2}{P}=\frac{(120V)^2}{2\times75W}=96\Omega$$
