לפני שאת נוגעת בתקע, תכבי את המפסק ותבדקי שאין חשמל.

Because the sentence is addressed to one woman.

You can see that in several words:

• שאת = you feminine singular
• נוגעת = touching / touch feminine singular
• תכבי = you will turn off / turn off feminine singular
• תבדקי = you will check / check feminine singular

If you were speaking to one man, it would be:

לפני שאתה נוגע בתקע, תכבה את המפסק ותבדוק שאין חשמל.

שאת is made of two parts:

• ש־ = that / when / which depending on context
• את = you feminine singular

So לפני שאת נוגעת literally means something like before that you touch / before you touch.

In Hebrew, ש־ is often attached directly to the next word, so:

• ש + את → שאת

This is very common in Hebrew after time words like לפני, אחרי, and often כש.

So לפני שאת נוגעת בתקע literally uses a present form, but in natural English it means before you touch the plug.

Hebrew often does this when talking about an action that is about to happen or is connected in time to another action.

A future-based version such as לפני שתגעי can also exist, but לפני שאת נוגעת is a very natural everyday pattern.

Not here. The verb לגעת normally takes the preposition ב־.

So:

• לגעת במשהו = to touch something

That means:

• נוגעת בתקע = touching the plug

So the ב־ here is required by the verb; it does not mean physical location in this sentence.

Also, בתקע is a contraction:

• ב + התקע → בתקע

So it is really ב־ + the plug.

It is the same spelling, but it is a different word.

In את המפסק, את is the direct object marker. It appears before a definite direct object.

So:

• תכבי את המפסק = turn off the switch

Here:

• את does not mean you
• it simply marks המפסק as the definite object of the verb

This is a very common learner confusion, because Hebrew has:

• אַתְ = you feminine singular
• אֶת = direct object marker

Same spelling, different job.

Because in modern Hebrew, the future tense is very often used to give commands, instructions, or polite directions.

So:

• תכבי = literally you will turn off, but here it means turn off
• תבדקי = literally you will check, but here it means check

Hebrew does have imperative forms:

• כבי
• בדקי

But in everyday modern usage, especially in instructions or safety language, the future forms are extremely common and often sound more natural.

שאין is also made of two parts:

• ש־ = that
• אין = there is not / there are not / there is no

So:

• תבדקי שאין חשמל = check that there is no electricity / no power

This is a very useful pattern:

• אני רואה שאין זמן = I see that there is no time
• בדוק שאין בעיה = check that there is no problem

Because אין is used to say that something does not exist / is not present in the present situation.

So:

• אין חשמל = there is no electricity / no power

By contrast, לא usually negates verbs:

• אני לא בודקת = I am not checking
• היא לא נוגעת = she is not touching

So in this sentence, the idea is not electricity does not do something, but rather electricity is absent. That is why אין is the correct choice.

Because חשמל here is being used in a general, mass-noun sense: electricity / power.

So:

• אין חשמל = there is no electricity / no power

This is the normal way to say it in Hebrew.

Adding ה־ would make it sound more specific, as if you meant the electricity in some particular sense. In most everyday situations, אין חשמל is exactly what Hebrew speakers say.

לפני can mean different things depending on context:

• before in time
• in front of in space

In this sentence, it clearly means before in time, because it is followed by a clause:

• לפני שאת נוגעת בתקע = before you touch the plug

So the sentence structure tells you that this is a time expression, not a location expression.