Quand le courant revient, je dois rallumer l’ordinateur et la lampe du salon.

In French, quand often takes the present tense when talking about something that happens regularly or whenever a situation occurs.

So Quand le courant revient means When the power comes back or Whenever the power comes back.

French often uses the present tense in places where English might also use the present:

• When he arrives, I leave.
• Quand il arrive, je pars.

This sentence sounds like a general situation or routine, not a one-time future event.

Je dois means I have to / I must in a general or immediate sense.

Here, the sentence describes what the speaker has to do whenever the power returns. That makes je dois very natural.

If you said je devrai, that would mean I will have to, which sounds more like a specific future situation:

• Quand le courant reviendra, je devrai rallumer l’ordinateur. = When the power comes back, I’ll have to turn the computer back on.

So:

• je dois = general rule, habit, or present obligation
• je devrai = specific future obligation

Here, le courant means the electricity supply or the power.

Even though courant can literally mean current, in everyday French le courant is commonly used to talk about electrical power in the house.

So:

• Le courant est coupé = The power is out
• Le courant revient = The power comes back

A native English speaker may expect something more like l’électricité, and that can also be used, but le courant is very common in this context.

Revenir means to come back, while retourner usually means to return/go back.

For electricity coming back, French normally says:

• Le courant revient

This is just the usual idiomatic choice.

So even though both verbs can relate to returning, revenir is the natural one here.

Allumer means to switch on / light.

Rallumer means to switch on again / relight.

Because the power was out, the computer and lamp were on before and now need to be turned on again. That is why rallumer is the best choice.

Compare:

• J’allume la lampe. = I switch on the lamp.
• Je rallume la lampe. = I switch the lamp back on / again.

The prefix re- often gives the idea of again, though it becomes ra- before some words:

• rallumer
• rappeler
• ramener

French uses articles much more often than English.

So where English might say:

• I have to turn the computer and lamp back on

French naturally says:

• je dois rallumer l’ordinateur et la lampe

In French, leaving out the articles here would sound wrong.

These articles can mean the in a specific sense, but they are also just part of normal French structure with nouns.

Du is the contraction of de + le.

So:

• de le salon becomes du salon

La lampe du salon means the lamp in the living room or more literally the living room’s lamp.

This is a very common French pattern:

• la porte du garage = the garage door
• la fenêtre du bureau = the office window
• la table du salon = the living room table

In everyday French, le salon usually means the living room or lounge.

So la lampe du salon is the living room lamp.

Be careful: English speakers sometimes associate salon with a hair salon, but in French that would usually need more context, such as salon de coiffure.

The sentence begins with a dependent clause:

• Quand le courant revient

Then it moves to the main clause:

• je dois rallumer l’ordinateur et la lampe du salon

In French, just as in English, a comma is often used after an introductory clause like this, especially when it comes first. It helps readability.

So the structure is:

• When the power comes back, I have to turn the computer and the living room lamp back on.

Because ordinateur starts with a vowel sound, le becomes l’ before it.

So:

• le ordinateur ❌
• l’ordinateur ✅

This is called elision. It happens very often in French:

• l’école
• l’ami
• l’idée

The same thing happens with other small words too, such as je becoming j’ before a vowel:

• j’arrive

Most naturally, it sounds like a general habit or repeated situation:

• whenever the power comes back, I have to turn the computer and the living room lamp back on.

That impression comes from:

• quand
  • present tense
• je dois in the present

If the speaker wanted to focus on one specific future event, French would more likely use the future tense:

• Quand le courant reviendra, je devrai rallumer l’ordinateur et la lampe du salon.

So the original sentence feels more like a routine or typical consequence.