Answer
a. The lower power setting
b. 15 $\Omega$
c. 9.9 $\Omega$
Work Step by Step
a. Use equation 18–6b to calculate the power, and solve for the resistance R.
$$P=\frac{V^2}{R}$$
$$R=\frac{V^2}{P} $$
We see that for a fixed voltage, the resistance is inversely proportional to the power. We expect that the lower power setting corresponds to a higher resistance.
b. Calculate R for the 950W setting.
$$R=\frac{V^2}{P}=\frac{(120V)^2}{950W}=15\Omega$$
c. Calculate R for the 1450W setting.
$$R=\frac{V^2}{P}=\frac{(120V)^2}{1450W}=9.9\Omega$$
Our intuition is confirmed.
