Can "effektiva" also mean effective, or do they differentiate between efficient and effective?
Generally, you don't. But if you want to be specific, you can use perhaps use the adjectives "ändamålsenlig" or "verkningsfull" to mean "effective".
Almost every time I redo a prior lesson the questions are different. That is good.
dem is the object form of the pronoun de, so it's for the same reason that you don't say "what makes they efficient" in English.
Its very important that efficient is its own word in physics, efficiency is the useful power output to total power input ratio. Having this word mean both efficient and effective may cause problems in physics.
Maybe they have different words in Swedish physics or they just use English words.
Yes, there are several related words in science. For instance, thermal efficiency is verkningsgrad, and effektivitet can be used synonymously for that. Power, however, translates to effekt.
No, "what does make them efficient" is grammatically correct but severely unidiomatic.
When hearing, but not seeing, this, is the only clue to it being 'dem' rather than 'de' the adjective that follows? i.e. Couldn't 'vad gör de ...' mean 'what do they do/make ...'? I misunderstood this sentence as 'What do they do efficiently?' but now I see it couldn't be that, because it finishes with an adjective rather than an adverb.
In a sense, but it's the same in English if that helps:
- vad gör dem effektiva = what makes THEM efficient?
- vad gör de effektivt = what make THEY efficiently?
(Obviously, "what do they make" is the idiomatic pick, so the example is just for emphasis.)
Yes - but if you're only hearing the Swedish and not seeing it, 'de' and 'dem' sound exactly the same, don't they? So it's only the ending of the adjective/adverb that tells you which it was??
Ah, yes. Since they're pronounced the same, only grammar will provide clues. In this case, it's the adjective, as you say.