Modern scales eschew weights and fulcrums in favor of electromagnets and even lasers.
FORBES: No. 15: The Scale
Current designs for maglev trains rely on electromagnets, since nobody has been able to make a permanent magnet strong enough to lift the weight of a train.
ECONOMIST: Maglev trains
These are small electromagnets interleaved at intervals along the track.
Electromagnets, however, bring problems of their own.
应用推荐
模块上移
模块下移
不移动