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There is a passage that I cannot understand. It is from one of the LSAT prep tests.

Superconductors are substances that conduct electricity without resistance at low temperatures. Their use, however, will never be economically feasible, unless there is a substance that superconducts at a temperature above minus 148 Celsius. If there is such a substance, that substance must be an alloy of niobium and germanium. Unfortunately, such alloys superconduct at temperatures no higher than minus 160 degrees Celsius.

For me, a sentence "If there ... germanium." seems to be saying that an alloy of niobium and germanium can superconduct at a temperature higher than minus 148. However, the last sentence ("Unfortunately...Celsius") says that such alloys cannot superconduct at a temperature higher than minus 160, so for me it sounds like this whole passage does not make sense.

The passage says that there should be a material that superconduct at higher temperature than -148 for economic feasibility, and alloy of niobium and germanium is the only material that could satisfy this requirement. Then, suddenly it says that such alloy cannot superconduct at higher temperature than -160 (which is also higher than -148). What am I understanding wrong here?

  • I think the issue is that you're not quite understanding the first bold sentence correctly. "If there is" is a hypothetical. It's not saying that an alloy like that does superconduct, it's saying that any alloy that superconducted above -148, if it did exist, would theoretically have to be made of niobium and germanium, because of the economic requirements. That said, I agree that the passage is a bit confusing and could be clearer. – stangdon Sep 26 '17 at 13:09
  • I'm voting to close this question as off-topic because I think you would be better of asking on Chemistry, if you want to know why alloys of niobidium don't superconduct at temperatures of 148K, the issue here is the science is confusing, not the English.. – James K Sep 26 '17 at 18:30
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If there is such a substance, that substance must be an alloy of niobium and germanium.

This is saying that (at least according to current knowledge of the materials) only an alloy of Nb and Ge could possibly have the characteristics needed to permit superconductivity at temperatures above (warmer than) 148 degrees C below zero (-148°C, 125K).

Unfortunately, such alloys superconduct at temperatures no higher than minus 160 degrees Celsius.

This is saying that (at least according to current knowledge of the materials) there is no alloy of Nb and Ge that will, in fact, permit superconductivity at a temperature warmer than 160 degrees C below 0 (-160°C, 113K).

Note that you have misunderstood the relationship of the temperatures: -160°C is colder (lower) than -148°C; this is why I included the conversion of the temperatures to Kelvins - with 0K being absolute 0 rather than the freezing point of water, there is no way that a temperature in Kelvins can be negative, and you can see that the conversion of -148°C is warmer (higher) than that of -160°C.

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The author is expecting you to fill in the "therefore Z" part of a "if X, but Y, therefore Z" pattern.

If there is such a substance, that substance must be an alloy of niobium and germanium.

Unfortunately, such alloys superconduct at temperatures no higher than minus 160 degrees Celsius.

[Therefore, there is not such a substance.]

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