![](http://u.dianyuan.com/bbs/u/34/1128495981.jpg?x-oss-process=image/watermark,g_center,image_YXJ0aWNsZS9wdWJsaWMvd2F0ZXJtYXJrLnBuZz94LW9zcy1wcm9jZXNzPWltYWdlL3Jlc2l6ZSxQXzQwCg,t_20)
500) {this.resized=true; this.width=500; this.alt='这是一张缩略图,点击可放大。\n按住CTRL,滚动鼠标滚轮可自由缩放';this.style.cursor='hand'}" onclick="if(!this.resized) {return true;} else {window.open('http://u.dianyuan.com/bbs/u/34/1128495981.jpg?x-oss-process=image/watermark,g_center,image_YXJ0aWNsZS9wdWJsaWMvd2F0ZXJtYXJrLnBuZz94LW9zcy1wcm9jZXNzPWltYWdlL3Jlc2l6ZSxQXzQwCg,t_20');}" onmousewheel="return imgzoom(this);">
r:磁棒半径
l:磁棒长度
各位大大请问一下….这公式中的b是指什么阿
还有ue=u0×120×5=4π×10(-7)×120×5,为什么还要乘以120的相对导磁系数和(1/d)=5 ,是因为材质的关系吗?还是几乎都是乘以这样的值
PS:希望各位大大帮忙解答一下