Learn Hardcore French: La lampe s’allume quand j’appuie sur l’interrupteur. - The lamp turns on when I press the switch.

Not literally. Here se marks a “middle/inchoative” voice: the subject undergoes a state change. Don’t translate se. It’s the same pattern as La porte s’ouvre (“The door opens”).

What’s the opposite of s’allumer?

Intransitive: s’éteindre (to go off/turn off by itself): La lampe s’éteint.
Transitive: éteindre (to switch off something): J’éteins la lampe.

Why is it j’appuie sur and not just j’appuie the switch?

For “to press,” French uses appuyer sur + noun. You must keep sur:

J’appuie sur l’interrupteur / sur le bouton.
Saying appuyer l’interrupteur is wrong in this sense. You can also say actionner un interrupteur (“operate a switch”).

How is appuyer conjugated here, and why the spelling change?

It’s a y→i stem change in the je/tu/il/ils forms:

je j’appuie, tu appuies, il appuie, nous appuyons, vous appuyez, ils appuient.
Future commonly: j’appuierai (also accepted: j’appuyerai).

What’s with all the apostrophes: j’appuie, s’allume, l’interrupteur?

It’s elision before a vowel sound or silent h:

je → j’ (j’appuie), se → s’ (s’allume), le/la → l’ (l’interrupteur).

What exactly is an interrupteur? Is it the same as a “button”?

An interrupteur is an electrical switch (often on a wall). A push-button is a bouton (or bouton-poussoir). A keyboard key is a touche. So you’d say appuyer sur le bouton but typically actionner/appuyer sur l’interrupteur.

Can I use lorsque instead of quand?

Yes. Lorsque ≈ quand (“when”) with the indicative. Lorsque is a bit more formal/literary; quand is the everyday default.

What tenses should I use if I mean a future time?

Use the future in both clauses:

La lampe s’allumera quand j’appuierai sur l’interrupteur.
(French doesn’t use the present for future time after quand as English often does.)

Why is there no comma before quand here?

In French, when the main clause comes first, you usually don’t put a comma before a following quand-clause. If you start with the quand-clause, you do use a comma:

Quand j’appuie sur l’interrupteur, la lampe s’allume.

Could I say si instead of quand?

You can, but it changes nuance:

Quand j’appuie… = whenever/when I press (temporal).
Si j’appuie… = if I press (conditional/hypothetical).

What’s the difference between la lampe, la lumière, and l’ampoule?

la lampe: the lamp/fixture.
la lumière: the light (illumination).
l’ampoule: the bulb.
So you can say La lampe s’allume (the device turns on) or La lumière s’allume (the light comes on).

Is there a difference between the action and the state, like “turns on” vs “is on”?

Yes:

Action/event: La lampe s’allume.
Resulting state: La lampe est allumée.
Opposite state: La lampe est éteinte.

Any pronunciation tips for tricky parts?

lampe: nasal vowel [ɑ̃] in lam.
s’allume: u is the front rounded vowel [y] (not like English “oo”).
j’appuie: [apɥi], with the glide [ɥ] (like “u” in “huit”).
interrupteur: initial nasal [ɛ̃], and eu as [œ].
quand j’…: the final -d of quand is silent before a consonant (no liaison): [kɑ̃ ʒapɥi].

Is it quand or quant?

Here it’s quand (“when”). Quant (with a t) means “as for” and is used in quant à (“as for…”).

Why la lampe and l’interrupteur (definite articles)? Could I use une or mon/ma?

Definite articles imply specific, known items (“the lamp,” “the switch”). You could say une lampe if introducing a non-specific lamp, or ma lampe if you mean “my lamp.” It depends on context, not grammar.

Is Ça s’allume okay, or should I use elle?

For a lamp, the correct pronoun is elle (feminine): Elle s’allume. Ça s’allume is casual and deictic (“That’s turning on”), fine in speech but less precise.

Any regional variations I should know?

In Québec and some regions, people often say ouvrir/fermer la lumière for “turn on/off the light.” In standard French (France), it’s allumer/éteindre la lumière.