turn on a fan的用法和样例：
- London taxis are easy to park because they turn on a sixpence.
- I wanted to take a turn on a bicycle.
- I turn on a switch but the light had burnt out.
- It was too dark, please turn on a torch.
- Rule 19: Trends rarely turn on a dime.
- The great speed of light explained why when we turn on a lamp in a dark room, the lamp and everything else in the room seem to light up at once.