Have you noticed that whenever the battery door or the memory card door is opened, Canon cameras will automatically turn OFF?
It's because the camera have detector switches on these doors. It's a way to protect the camera when you change battery or memory card.
But if you change the lens, the camera is remains ON. It means no protection required when changing lens
May I suggest that, in addition to properly naming your threads, you please also learn how to use the search engine. P.S. proper spelling helps there. It's "lens" and not "lans".
Your question has been asked many times before. Here are some example threads from a very simple search: