Okay, for example
The bar magnet is moved back and forth.
Why is 'moved' used? Since it is a present tense, should it be 'move' instead?
Why are you wrong?
Why were you wrong?
Like because I asked my classmate when we were looking at our papers but then I asked him ‘why are you wrong?’ then I suddenly doubt about it since he had made the mistake earlier, should it be ‘why were you wrong?’