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广大同学在运用二次方程(组)求解物理问题时,易形成思维定势,即:对所得的两个(组) 根,从数学、物理、实际生活等角度,对它们进行取舍.但是,是否必须要舍掉一个(组)根呢?若能从物理角度对两根仔细再分析,充分利用两根提供的信息,把握其物理本质,打破思维定势,定能使思路开阔;提高解题能力. 例1 如图1所示,电源电动势ε=12V,内电阻r=0.5Ω,定值电阻R1=3.5Ω,在电键S断开或闭合时,外电路中的αb间消耗的功率都是8W,则电键S闭合后通过R2的电流是_A. 解析:法1 根据两种情况下,αb间消耗功
When students use quadratic equations (groups) to solve physics problems, they tend to form a fixed mindset, that is, to make choices about the two (groups) roots obtained, and from mathematics, physics, and practical life, etc. However, Is it necessary to abandon one (group) root? If we can re-analyze the two carefully from the physical point of view, make full use of the information provided by the two to grasp its physical nature, break the mindset, will be able to open the mind; improve the solution Problem 1. Example 1 As shown in Fig. 1, the power EMF ε = 12V, the internal resistance r = 0.5Ω, and the setting resistor R1 = 3.5Ω, the power consumed between αb in the external circuit when the key S is opened or closed Both are 8W, then the current through the R2 after the key S is closed is _A. Resolution: Method 1 Under the two conditions, the power consumption between αb