对一道初中电学题的商榷

• 作 者: 顾建平
• 机 构: 江苏吴江八坼中学!215222
• 出 处: 物理教师
• 发表日期: 1997年12期
• 关键词: 初中物理 滑动变阻器 示数 道初 电源电压 参考答案 滑片 有效电阻 江苏吴江 消耗功率

某出版社出版的《新编初中物理试卷》(三年级下学期)中有一道电学题如下:在图示(图1所示〕电路中,电源电压保持不变,当滑动变阻器的滑片P向右移动时,灯L的亮度将_______.(填“变亮”、“不变”或“变暗”),电压表的示数将______(填“变大”、“不变”或“变小”),滑动变阻器R上消耗的电功率将_____、参考答案是:灯L的亮度将变亮,电压表示数将变小,R上消耗的电功率将变小.笔者认为对R上消耗的电功率变小这个答案不妥,因为此题缺少讨论R上消耗电功率的条件.

In the “New Junior High School Physics Examination Paper” (second semester of the third grade) published by a certain publishing house, there is an electric problem as follows: In the illustrated circuit (shown in Fig. 1), the power supply voltage remains the same, when the sliding varistor slides P When moving to the right, the brightness of the lamp L will be _______. (filling “brightens”, “changing” or “darkening”) and the voltmeter indication will be ______ (filling “bigger”, “unchanged” Or “smaller”), the electrical power consumed by the sliding rheostat R will be _____, and the reference answer is: the brightness of the lamp L will become bright, the voltage representation number will become smaller, and the electric power consumed on the R will become smaller. The answer to the fact that the consumed electric power is getting smaller becomes unsatisfactory, because this question lacks the conditions for discussing the electric power consumed on R.