Learn Hardcore Russian: Эксперимент проводился несколько часов подряд. - The experiment was conducted for several hours in a row.

Часов is in the genitive plural. In Russian, quantifiers like несколько (“several”) always require the following noun to be in the genitive plural to express an indefinite quantity.

What is подряд doing in this sentence?

Подряд is an adverb meaning “in a row” or “consecutively.” It modifies the duration phrase несколько часов, emphasizing that those hours came one after another without a break.

Why is проводился used instead of an active verb form?

Проводился is the passive imperfective past tense of проводить (“to conduct”). Using the passive voice keeps the focus on the experiment itself rather than on who performed it. If you wanted to name the doer, you could say, for example, Эксперимент проводился учёными…

What aspect does проводился express, and why is that aspect chosen?

It’s the imperfective aspect, which highlights the ongoing nature or duration of the experiment. The speaker wants to stress that the experiment was taking place continuously over several hours, not just that it was completed.

How is несколько часов подряд different from в течение нескольких часов?

Both mean “for several hours,” but в течение нескольких часов simply states the time span, whereas несколько часов подряд with подряд specifically conveys that the hours were back-to-back without interruption.

What’s the difference between проводился and был проведён?

Проводился (imperfective passive) stresses the process or duration of conducting the experiment.
Был проведён (perfective passive) stresses the fact that the experiment was completed.
You would not normally say Эксперимент был проведён несколько часов подряд, because perfective leans toward a finished action rather than continuous activity.

What part of speech is несколько here?

Несколько is a numeral-quantifier (sometimes called an indefinite pronoun) that expresses “several” or “a few.” It modifies the noun часов by specifying an approximate small quantity.

Can I change the word order to Несколько часов подряд проводился эксперимент?

Yes. Russian word order is flexible. Placing несколько часов подряд at the beginning foregrounds the duration, while putting эксперимент first foregrounds the experiment itself. The basic meaning stays the same.

Could I use часами напролёт instead of несколько часов подряд?

Absolutely. You could say Эксперимент проводился часами напролёт. Here часами is in the instrumental plural and напролёт is another adverb meaning “straight through,” so it conveys the same idea of working for hours on end.

Why is there no preposition в before несколько часов подряд, whereas other time constructions use в?

When you indicate duration with a quantity (e.g. три часа, несколько часов), you use the genitive case without a preposition. If you switch to a construction like в течение, you must use в plus the genitive (e.g. в течение нескольких часов).