【2017年整理】交变电流的产生及变化规律.ppt

*3．如图所示，一单匝闭合线框 在匀强磁场中绕垂直于磁场 方向的转轴匀速转动，转动 过程线框中产生的感应电 动势的瞬时值为e＝0.5sin 20t(V)，由该表达式可推知以下哪些物理量( ) A．匀强磁场的磁感应强度 B．线框的面积 C．穿过线框的磁通量的最大值 D．线框转动的角速度 CD Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. BD Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. BCD Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. 第1节　交变电流的产生及变化规律 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. 1．交变电流的产生：将矩形线圈置于 中，并绕垂直于磁感线的轴 ，线圈中就会产生正(余)弦交变电流． 2．中性面： (1)线圈位于中性面时，穿过线圈的磁通量 ，磁通量的变化率为 ，感应电动势为 ． (2)线圈转动一周， 次经过中性面，线圈 ，电流的方向就改变一次． 匀强磁场 匀速转动 最大 零 零 两 每经 过中性面一次 一、交变电流的产生及变化规律 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. Emsinωt NBSω Imsinωt 某一时刻 热效应 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. 快慢 一次周期性 次数 0.02 50 100 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. 【思路点拨】线圈从垂直于中性面位置启动，则瞬时值的表达式为余弦函数．由此构造出瞬时值表达式，可求出电动势的最大值，然后是有效值，再到功率，从而完成A、B、C的筛选；再画出线圈转动的截面图，可知其磁通量变化规律确是正弦函数，但对线圈的最大磁通量，即BS的计算有误，即排除D项． Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. 【答案】AC Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. 元贝驾考 元贝驾考2016科目一 科目四驾考宝典网 / 驾考宝典2016科目一 科目四 Evaluati