teiden no toki ha, kaityuudentou wo tukatte heya wo akaruku simasu.

停電 means power outage / blackout, and とき means time / when.

So:

• 停電のとき = when there is a power outage / at the time of a blackout

The の connects the noun 停電 to とき. A very literal way to think of it is:

• the time of a power outage

Then は marks that whole phrase as the topic:

• As for when there is a power outage, ...
• In the event of a power outage, ...

So 停電のときは sets the situation or topic for the rest of the sentence.

Because 停電 is a noun, and とき is also a noun.

In Japanese, when one noun modifies another noun, の is often used:

• 雨のとき = when it rains / at the time of rain
• 子どものとき = when I was a child / in childhood
• 停電のとき = when there is a power outage

So here, の works like of or a noun-linker. It turns 停電 into something that can describe とき.

Good question. Both は and に can appear with time expressions, but they do different jobs.

• に marks a specific time point: at / on / in
• は marks the topic: as for...

In this sentence, 停電のときは is not just giving a time; it is setting up a situation and saying what one does in that situation.

So the nuance is:

• 停電のときは、... = When there is a power outage, as a general rule / in that case, ...

If you used に, it would sound more like simply locating the action in time:

• 停電のときに、懐中電灯を使って...

That is also possible, but は is very natural when introducing a condition or situation and then explaining what happens or what one does.

使って is the て-form of 使う (to use).

The て-form can connect actions, often meaning something like:

• use X and...
• by using X...
• using X...

So:

• 懐中電灯を使って部屋を明るくします = use a flashlight to make the room bright = make the room bright by using a flashlight

Here, 使って connects the method to the main action:

• method: 懐中電灯を使って = using a flashlight
• main action: 部屋を明るくします = make the room bright

Because the sentence is expressing causing a change, not just describing a state.

Compare:

• 部屋が明るいです = The room is bright.
  This describes the room's condition.

• 部屋を明るくします = Make the room bright.
  This means someone causes the room to become bright.

So in your sentence, the speaker is saying what they do during a power outage:

• They use a flashlight
• in order to make the room bright

That is why the verb pattern is adjective + く + する.

This uses a very common pattern:

• い-adjective stem + くする = make something ...

Here:

• 明るい = bright
• remove the final い and add く → 明るく
• then add する → 明るくする

So:

• 部屋を明るくする = to make the room bright

Other examples:

• 部屋を広くする = make the room spacious
• 音を大きくする = make the sound louder
• 値段を安くする = make the price cheaper

In this sentence, します is the polite form of する.

Because 部屋 is the thing being affected by the action 明るくします.

In Japanese, を does not only mark a direct object in the English sense of eat something or buy something. It also marks the thing that is changed by a make something X pattern.

So:

• 部屋を明るくする = make the room bright
• 髪を短くする = make the hair short / cut the hair short
• 音を小さくする = make the sound quieter

The room is the thing being changed, so it takes を.

Yes, 懐中電灯 means flashlight (or torch in British English).

Its reading is:

• かいちゅうでんとう

This is a compound word:

• 懐中 = in one's pocket / carried on the person
• 電灯 = electric lamp

So historically it is something like portable electric lamp, but in normal modern usage it just means flashlight.

The subject is omitted, which is very normal in Japanese.

The sentence does not explicitly say I, we, people, or you. The implied subject depends on context. It could mean things like:

• I use a flashlight to light the room during a power outage.
• We use a flashlight to light the room during a power outage.
• During a power outage, people use a flashlight to make the room bright.

Japanese often leaves out subjects when they are understood from the situation.

Yes, very naturally.

A literal translation is:

• make the room bright

But in smooth English, you would often say:

• light the room
• light up the room

That is a natural translation choice. Grammatically, though, Japanese is using the make + adjective structure.

Usually, it sounds more like a general statement or habitual instruction, especially because of 停電のときは.

It has a sense like:

• When there is a power outage, we use a flashlight to light the room.
• In the event of a blackout, use a flashlight to light the room.

Without more context, it does not strongly point to one single blackout. It sounds more like a general rule, explanation, or instruction.

Yes, to some extent. Japanese word order is flexible as long as the particles make the roles clear.

For example, these are possible:

• 停電のときは、懐中電灯を使って部屋を明るくします。
• 停電のときは、部屋を懐中電灯を使って明るくします。

The first version is more natural and easier to follow.

Japanese often puts the setting first, then the method, then the main action:

1. when there is a power outage
2. using a flashlight
3. make the room bright

That is exactly the order used in your sentence.

Yes, though both can work in many contexts.

• 懐中電灯を使って = using a flashlight
• 懐中電灯で = with a flashlight / by flashlight

The を使って version is a little more explicit because it directly says use.
The で version is shorter and focuses on the tool or means.

So these are both natural:

• 懐中電灯を使って部屋を明るくします。
• 懐中電灯で部屋を明るくします。

The original sentence sounds slightly more explanatory because it spells out the action of using the flashlight.