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

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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