问题 选择题

在磁感应强度为B0、方向竖直向上的匀强磁场中,水平放置一根长通电直导线,电流的方向垂直于纸面向里.如图所示,a、b、c、d是以直导线为圆心的同一圆周上的四点,在这四点中(  )

A.b、d两点的磁感应强度相等

B.a、b两点的磁感应强度相等

C.c点的磁感应强度的值最小

D.b点的磁感应强度的值最大

答案

用右手螺旋定则判断通电直导线在abcd四个点上所产生的磁场方向,如图所示:

a点有向上的磁场,还有电流产生的向上的磁场,电流产生的磁感应强度和原磁感应强度方向相同,叠加变大.

b点有向上的磁场,还有电流产生的水平向左的磁场,磁感应强度叠加变大,方向向左上.

c点电流产生的磁感应强度和原磁感应强度方向相反,叠加变小.

d点有向上的磁场,还有电流产生的水平向右的磁场,叠加后磁感应强度的方向向右上.d点与b点叠加后的磁场大小相等,但是方向不同.

选项ABD错误,选项C正确.

故选C.

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