El ordenador está encendido cuando estudio en mi cuarto.

The computer is on when I study in my room.

Breakdown of El ordenador está encendido cuando estudio en mi cuarto.

• yo: I
• en: in
• mi: my
• estar: to be
• cuando: when
• estudiar: to study
• el cuarto: the room
• el ordenador: the computer
• .: period
• encendido: on

Questions & Answers about El ordenador está encendido cuando estudio en mi cuarto.

Why is it el ordenador and not la computadora?

Both mean computer, but they’re used in different regions:

• In Spain, the normal word is el ordenador.
• In most of Latin America, people say la computadora.

Since you’re learning Spanish from Spain, el ordenador is the natural choice here.

Why is ordenador masculine (el) and not feminine?

In Spanish, every noun has a grammatical gender that you just have to learn.

• Ordenador is masculine, so it takes el and masculine adjectives:
  
  • el ordenador encendido, un ordenador nuevo
• There’s no logical reason; it’s just the way the word has developed in the language.

Why is it está encendido and not es encendido?

The verb estar is used for temporary states or conditions. Here, being switched on is a temporary state:

• El ordenador está encendido. – The computer is on (right now / at that time).

Using ser (es encendido) would sound wrong in this context; it would suggest a permanent characteristic, which doesn’t fit. So for things like on/off, open/closed, clean/dirty you normally use estar in Spanish.

Is encendido an adjective here or a verb form?

It looks like a past participle of encender (to switch on), but in this sentence it functions as an adjective describing the state of the computer:

• Verb: encender el ordenador – to switch on the computer
• Resulting state: el ordenador está encendido – the computer is on

So grammatically: estar + encendido = to be in the “on” state.

Why encendido and not a word that looks like “on”, like en or sobre?

English uses on both for location and power state:

• The book is on the table.
• The computer is on.

Spanish separates these ideas:

• Location: en (in/on), sobre (on top of)
• Power state: encendido (switched on), apagado (switched off)

So for “The computer is on” (powered on), you must say El ordenador está encendido, not El ordenador está en or … está sobre.

Why is it está encendido and not está encendida?

The adjective encendido/encendida has to agree with the noun it describes:

• ordenador is masculine singular, so: encendido
• If the noun were feminine, e.g. la lámpara, you’d say: La lámpara está encendida.

So:
El ordenador está encendido. (masc. sing.)
Las luces están encendidas. (fem. plural)

Why is it cuando estudio and not cuando estoy estudiando?

Here, the idea is a habitual situation: whenever you study, the computer is on.

In Spanish:

• For general habits or repeated actions, use the simple present:
  
  • cuando estudio – when I study (whenever I study)
• The present continuous (estoy estudiando) focuses on what is happening right now.

So:

• El ordenador está encendido cuando estudio en mi cuarto.
  = The computer is on whenever I study in my room.
  If you said cuando estoy estudiando, it would sound more like talking about a specific ongoing situation.

Why is there no yo before estudio?

Spanish verb endings already show the subject:

• estudio = I study
• estudias = you study
• estudia = he/she/it studies

Because estudio clearly means I study, the subject pronoun yo is usually omitted unless you want to emphasize it:

• Normal: Cuando estudio en mi cuarto…
• Emphasizing: Cuando yo estudio en mi cuarto… (e.g. contrasting with when someone else studies)

Can you change the order of the two parts of the sentence?

Yes, both word orders are natural in Spanish:

• El ordenador está encendido cuando estudio en mi cuarto.
• Cuando estudio en mi cuarto, el ordenador está encendido.

The meaning is the same. Starting with cuando… just gives a slightly different emphasis, but both are correct and common.

Why is it en mi cuarto and not en el mi cuarto?

With possessive adjectives like mi, tu, su, nuestro, you do not use a definite article in front of them:

• mi cuarto – my room
• tu casa – your house
• nuestra escuela – our school

So en mi cuarto is correct.
en el mi cuarto is not standard Spanish and sounds wrong.

What’s the difference between cuarto, habitación, and dormitorio?

All can refer to a room, but there are nuances:

• cuarto – very common and general: room; in this context often understood as bedroom
• habitación – also room; a bit more neutral/formal; often used in hotels
• dormitorio – specifically bedroom (place where you sleep)

In everyday Spain Spanish, saying mi cuarto to mean my bedroom is very common and natural.

Why is estudio in the indicative and not the subjunctive (e.g. cuando estudie)?

With cuando, Spanish uses:

• Indicative for habitual / repeated / factual actions:
  
  • Cuando estudio en mi cuarto, el ordenador está encendido.
    (Whenever I study in my room, the computer is on.)
• Subjunctive for future, not-yet-realized actions (often after a future reference):
  
  • Cuando estudie en mi cuarto, encenderé el ordenador.
    (When I study in my room [in the future], I’ll switch on the computer.)

Your sentence talks about a regular situation, so indicative (estudio) is correct.

Could I use mientras instead of cuando here?

You can, but the nuance changes slightly:

• cuando estudio en mi cuarto – when/whenever I study in my room
• mientras estudio en mi cuarto – while I am studying in my room

So:

• El ordenador está encendido cuando estudio en mi cuarto.
  Focus on the time or occasion.
• El ordenador está encendido mientras estudio en mi cuarto.
  Focus on the fact that the computer is on during the whole period you are studying.

Both are grammatically correct; choice depends on the nuance you want.