关 (guān) is a general verb for 'close, shut, turn off' — used for doors, windows, TVs, etc. For devices specifically, use 关机 (guān jī) as a verb-object compound. In formal/written contexts, 关闭 (guān bì) is more appropriate; to lock with a key, use 锁 (suǒ), and to confine animals/people in an enclosure, use 圈 (juān).