Answer
a. The power decreases.
b. The power increases.
Work Step by Step
a. The power consumed may be written as $P=\frac{V^2}{R}$. The temperature coefficient of resistivity for copper is positive, so the resistance of the copper heating element increases as it heats up. An increasing resistance connected to a constant voltage source decreases the power consumed.
b. The power consumed may be written as $P=\frac{V^2}{R}$. The temperature coefficient of resistivity for carbon is negative, so the resistance of the carbon cylinder decreases as it heats up. A decreasing resistance connected to a constant voltage source increases the power consumed.
