Final answer:
The temperature coefficient of resistivity measures how the resistivity of a material changes with temperature.
Step-by-step explanation:
The temperature coefficient of resistivity is a measure of how the resistivity of a material changes with temperature. It is given by the formula:
α = (ρ - ρ0) / (ρ0ΔT)
where α is the temperature coefficient of resistivity, ρ is the resistivity at a certain temperature, ρ0 is the resistivity at a reference temperature, and ΔT is the temperature change. To find the temperature coefficient of resistivity at 20°C for the material of the rod, you will need the resistivity at 20°C and the resistivity at a reference temperature.