问题 计算题

如图所示,单匝矩形线框的ab边长l1=20cm,bc边长l2=10cm,线框电阻R=2.0Ω,置于B=0.3T的匀强磁场中,磁感线方向与线框平面垂直,ad边恰好处于磁场边缘。若用力拉动线框,使线框沿图中箭头所示方向以v=10.0m/s的速度做匀速直线运动。求:

(1)线框中感应电流的大小;

(2)线框bc边所受的安培力的大小和方向;

(3)在把整个线框拉出磁场外的过程中,外力所做的功。

答案

解:(1)线框中感应电动势为:E=Bl2v 

则感应电流I ==0.15A   

(2)bc边所受的安培力:F=BIl2=4.5×10-3N,方向向右 

(3)因线框匀速运动,外力的大小F'等于线框受到的安培力F,即F'=F 

外力所做的功:W=F'I=BIl2l1=9.0×10-4J

阅读理解

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请仔细阅读下面有关信息。

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匹配信息

你打算为你的朋友Mike, Mary, Robert, Lily和Tom选购新年礼物。请阅读有关对他们的描述,选出最适合他们的礼品。

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