Learn Hardcore Italian: Il nuovo lampadario è stato acceso dal tecnico per testare la luce. - The new chandelier was switched on by the technician to test the light.

You take the auxiliary verb essere in the desired tense and add the past participle of the main verb, which then agrees in gender and number with the subject. Here: essere (è) + past participle acceso.

Why is the agent introduced by da in dal tecnico?

In Italian passive constructions, the doer of the action (the “agent”) is introduced by da (“by”). Since il tecnico is masculine singular, da + il contracts to dal.

Couldn’t you say da il tecnico instead of dal tecnico?

No. Italian always contracts da + il into dal, da + lo into dallo, da + la into dalla, etc.

Why is nuovo placed before lampadario? Couldn’t it be il lampadario nuovo?

Many adjectives in Italian can go before or after the noun. Placing nuovo before makes it a more inherent characteristic (“the new chandelier” as opposed to “another one that happens to be new”). Both orders are grammatically correct, but il nuovo lampadario sounds more natural here.

What’s the nuance between testare and provare la luce?

Testare specifically means “to test” or “to check performance,” often used with equipment. Provare is more general (“to try”). You could say provare la luce, but testare la luce emphasizes a technical check.

How would I say this sentence in the active voice?

You’d flip agent and subject:
Il tecnico ha acceso il nuovo lampadario per testare la luce.
Here ha acceso is the active passato prossimo (“turned on”).

Can I use a different verb for “to turn on” in Italian?

Accendere is the standard. Some dialects or contexts might use mettere su (for records, machines) or attivare (for systems), but for lights, accendere is the correct choice.