CAREFUL about the use of the words ON and OFF in physics, which remember is a precise subject:
we do NOT turn switches on or off, we CLOSE or OPEN a switch which respectively turns the CIRCUIT ON or OFF.

Often in common use of language, you may hear a bell (such as the end of a lesson) and say something like "that's the bell going off" or "is that an alarm going off?". What you really mean is that is the bell going ON!!! so it is best to use an expression such as "the bell is ringing" or "the alarm sounds". sorry, but what sounds right when you say it actually is read as the exact opposite when it is written!

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