One way this might be done is to place a grid of wires behind them and induce a magneticfield where the wires cross. The spheres at the intersections would then rotate.
方法之一，有可能是在其背后建立一网格线和在线经过的地方引入磁场，在这地方的微珠就可以旋转了。
2
One way this might be done is to place a grid of wires behind them and induce a magneticfield where the wires cross.
有一种也许可行的方法，就是在其后放置一线网，在叉线处引入磁场。
3
In this paper, the calculating formulas of magneticfield for long current carrying conductor with any form of cross-section are deduced with the help of magnetic vector potential.