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在中学物理教学中由于对电力线的性质强调得不够,常常会有意或无意地画出一些错误的电力线图,在若干书刊中也屡见不鲜。今聊举数例,并附分析供参考。例1、如图1示所。 [分析] 导体在施感电荷的作用下,左端感应有负电,右端感应有等量正电,并在电场中处于静电平衡状态,整个导体就变成了等势体。在图1中如有电力线由A至B(或由C至D),则A、B(或C、D)两点间必然会存在电势差:U_(AB)=∫_A~BE·dl(或U_(CD)=∫_c~vE·dl)。这与静电平衡时导体是等势体相矛盾。所以图1所示的电力线图是错误的。
In the middle school physics teaching, because of the insufficient emphasis on the nature of the power line, it is often consciously or unintentionally drawn some wrong power line diagrams, which are also common in several books and periodicals. There are several examples of this chat, with analysis for reference. Example 1, as shown in Figure 1. [Analysis] Under the effect of the inductive charge, the conductor is negatively charged at the left end and has the same amount of positive charge at the right end, and is in an electrostatic equilibrium state in the electric field, and the entire conductor becomes an equipotential body. In Fig. 1, if there is a power line from A to B (or from C to D), there is bound to be a potential difference between A, B (or C, D): U_(AB)=∫_A~BE·dl (or U_(CD)=∫_c~vE·dl). This is inconsistent with the equipotential body when the electrostatic balance is in place. So the power line diagram shown in Figure 1 is wrong.