Temperature coefficients of resistivity are given in Table 25.2.

(a) If a copper heating element is connected to a source of constant voltage, does the electrical power consumed by the heating element increase or decrease as its temperature increases? Explain.

(b) A resistor in the form of a carbon cylinder is connected to the voltage source. As the temperature of the cylinder increases, does the electrical power it consumes increase or decrease? Explain.

Table 25.2

Temperature Coefficients of Resistivity (Approximate Values Near Room Temperature) a [(C)-'] 0.0039 a [(C)-'] Material Material Aluminum Lead Manganin Mercury Nichrome Silver Tungsten 0.00000 0.00088 0.0004 0.0038 0.0045 Brass 0.0020 Carbon (graphite) Constantan Copper 0.00001 0.00393 0.0050 Iron