The electricfield, magneticfield and electromagnetic force have better penetrated ability but less near-wall strength whiles the propulsion units of wider magnetic poles.
电磁条带较宽的推进单元体所激发的电场，磁场和电磁力都具有更好的渗透效果，但相应同深度场强值较小。
2
In 1832, the year of Michael Faraday's discovery that a changing magneticfield produces an electric field, a young French engineer patented a new and more efficient waterwheel.
He also realised that varying the strength of an electricfield would generate a changing magneticfield, even in empty space with no moving electric charges to speak of.