1. The solar cell could change sunlight directly into electricity.
2. The solar cell could directly change sunlight into electricity.
(Are both acceptable? What is the suitable position of 'directly'? Which one is right?)
Both are correct because adverbs can often be used several places in a sentence. I much prefer # 1.
Both sentences are grammatically correct and convey the same meaning. The word "directly" in these sentences is an adverb that modifies the verb "change," indicating that the transformation of sunlight into electricity happens without any intermediary steps or processes.
In terms of suitable positioning, adverbs can generally be placed before or after the verb they modify. In this case, "directly" can be placed either before or after "change" in the sentence. Therefore, both sentences are correct, and the choice between them depends on personal preference or stylistic considerations.