题目3单选题
如图所示,边长为l的正方形导线框abcd,在磁感应强度为B的匀强磁场中以速度v垂直于bc边在线框平面内平动,磁场方向与线框平面垂直,设整个线框中的总的感应电动势为ξ,bc两点间的电势差为u,则 <img src="https://tihai-oss-cloud.itihey.com/img/375b91bda510b8e13f0cd97b7eba150c.jpg">A. ξ =Blv, u = BlvB. ξ =Blv, u = 0C. ξ =0, u = BlvD. ξ =0, u = 0