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: Power ($P = I^{2}R$) depends on current ($I$) and resistance ($R$). Since the observation is about resistance dropping to zero (not about power calculation with current), this option is incorrect.
• Temperature: The temperature is the condition (cooling) for the resistance change, not the main observation. The main observation is about the resistance property.
• Intensive property: An intensive property does not depend on the amount of substance. Resistance is an intensive property (for a given material, its resistivity - related to resistance - is intensive). When the material is cooled and resistance drops to zero (a property of the material itself, not depending on the amount of the superconducting material), it is an intensive property observation.
• Extensive property: An extensive property depends on the amount of substance (e.g., mass, volume). Resistance (related to resistivity, which is intensive) is not an extensive property in the context of the material's inherent property (dropping to zero when cooled, regardless of the sample size).

Answer:

The scientist is observing an intensive property of a superconductor.