Question

a scientist observes that the electrical resistance of a superconducting material drops to zero when the material is cooled to very low temperatures. which of the following statements best describes what the scientist is observing?
the scientist is observing the electrical power of a superconductor.
the scientist is observing the temperature of a superconductor.
the scientist is observing an intensive property of a superconductor.
the scientist is observing an extensive property of a superconductor.

Explanation:

• Electrical power \(P = I^{2}R\). If \(R = 0\), \(P=0\), but the observation is about \(R = 0\) (a property), not power calculation.
• Temperature is the variable being changed (cooling), not the property being observed (resistance).
• Intensive properties do not depend on the amount of substance. Resistance being zero at low - temps is a property of the material (superconductor) itself, not depending on the quantity of the superconductor.
• Extensive properties depend on the amount of substance (e.g., mass, volume). Resistance being zero is not an extensive property.

Answer:

The scientist is observing an intensive property of a superconductor.