Answer
See answers.
Work Step by Step
a. Calculate the resistance at the operating temperature from the power and voltage.
$$P=\frac{V^2}{R}$$
$$R=\frac{V^2}{P}=\frac{(120V)^2}{75W}=190\Omega$$
b. Calculate the resistance at room temperature is found by using equation 18–4.
$$R=R_0(1+\alpha(T-T_0))$$
$$R_0=\frac{R}{(1+\alpha(T-T_0))}=\frac{192\Omega}{1+(0.0045K^{-1})(2800K-293K)}\approx16\Omega$$
