Self-study
Superconductors are substances that conduct electricity without resistance at low temperatures. █████ ████ ████████ ████ █████ ██ ████████████ █████████ ██████ █████ ██ █ █████████ ████ █████████████ ██ █ ███████████ █████ █████ ███ ███████ ████████ ██ █████ ██ ████ █ ██████████ ████ █████████ ████ ██ ██ █████ ██ ███████ ███ ██████████ ██████████████ ████ ██████ ████████████ ██ ████████████ ██ ██████ ████ █████ ███ ███████ ████████
Summary
The stimulus can be diagrammed as follows:
Notable Valid Inferences
A superconductor cannot be economically feasible. Two necessary conditions of an economically feasible superconductor are that it superconducts at or above -148 degrees Celsius, and that it superconducts no higher than -160 degrees Celsius. These two necessary conditions contradict each other, so we can never have an economically feasible superconductor.
7.
If the statements above are █████ █████ ███ ██ ███ █████████ ████ ████ ██ █████
a
The use of ███████████████ ████ █████ ██ ████████████ █████████
This must be true. An economically feasible superconductor involves two contradictory necessary conditions: it must operate above -148°C and yet not operate above -160°C (which is a lower temperature than -148°C). This is impossible. So we can never fulfill the sufficient condition.
b
If the alloys ██ ███████ ███ █████████ ██ ███ ████████████ ██ ████████████ █████ █████ ███ ███████ ████████ ████ █████ ███ █████ ██████████ ████ ████ ██ ███
This could be false. The stimulus does not provide any information about other substances and their capabilities to superconduct.
c
The use of ███████████████ █████ ██ ████████████ ████████ ██ █████ ██ █ █████████ ████ █████████████ ██ ████████████ █████ █████ ███ ███████ ████████
This could be false. (C) can be diagrammed as “There is a substance that superconducts at temperatures below -140 degrees Celsius→ use of superconductors is economically feasible.” This is not consistent with our diagram.
d
Alloys of niobium ███ █████████ ██ ███ ████████████ ██ ████████████ █████ █████ ███ ███████ ████████
This must be false. We know that alloys of niobium and germanium superconduct at temperatures no higher than -160 degrees Celsius.
e
No use of ██████ ██ ███████ ███ █████████ ████ ████ ██ ████████████ █████████
This could be false. We only discuss alloys of niobium and germanium with regards to their potential use as superconductors; we don’t have any information about potential other uses.