Learn Hardcore Spanish (Latin America): Un científico explicó un experimento usando un imán muy fuerte. - A scientist explained an experiment using a very strong magnet.

Explicó is the third-person singular preterite of explicar, used to describe a completed action in the past. The speaker is narrating that “a scientist explained an experiment” at a specific point in time. If you used the present (explica), it would sound like a general fact or ongoing action. The imperfect (explicaba) would emphasize an ongoing or habitual past action, not a single completed event.

Why does the sentence use un científico (an indefinite article) rather than el científico (the definite article)?

Using un científico means “a scientist,” referring to any unspecified scientist. El científico would be “the scientist,” implying that the listener already knows which scientist is meant. Since this sentence introduces the scientist for the first time or doesn’t single out a particular individual, the indefinite article un is appropriate.

What role does the gerund usando play in this sentence?

Usando is a gerund functioning adverbially to express the means or manner of the action. It tells us how the scientist explained the experiment—namely, by using a very strong magnet.

Could I replace usando with the preposition con?

Yes. You can say:
“Un científico explicó un experimento con un imán muy fuerte.”
Here con + noun also indicates the instrument or means. Both versions are correct; usando highlights the action (“using”), while con is more neutral (“with”).

Does usando un imán muy fuerte modify the verb explicó or the noun experimento?

It modifies the verb explicó, describing how the explanation took place. It is not saying that the experiment itself used the magnet, but that the act of explaining was done through the use of a strong magnet.

Why is muy fuerte placed after imán rather than before?

In Spanish, most adjectives follow the noun they modify. So you say imán fuerte (“strong magnet”). Adding muy (“very”) before the adjective is the normal way to intensify it: imán muy fuerte.

Can I use a different adjective instead of fuerte, such as potente or poderoso?

Yes. All of these are synonyms in this context. For example:
“Un científico explicó un experimento usando un imán muy potente.”
or
“…un imán muy poderoso.”
Each choice has a subtly different flavor, but they all convey “a magnet with a lot of strength.”

What’s the difference between usando and para usar in this context?

Usando indicates the means or manner (“by using”).
Para usar would indicate purpose (“in order to use”). So:
• …explicó… usando un imán… = He explained by using a magnet.
• …explicó… para usar un imán… = He explained in order to use a magnet (which sounds odd here, because explanation isn’t normally done to achieve the use of a magnet).

Could I rewrite the sentence as “Un científico explicó un experimento que usaba un imán muy fuerte”?

Yes, but the meaning shifts.
• Original: the scientist’s explanation involved a very strong magnet.
• Rewritten: the experiment itself used a very strong magnet (it describes the experiment’s design, not the way it was explained). Choose the structure based on what you want to emphasize.