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本刊1992年第3期刊登的《高中物理综合测试题》,多重选择题中有这样一题: 如图所示,A为一固定的超导体圆环,一条形磁铁从右侧无穷远处沿环轴线移向圆环,穿过后移到左侧无穷远处,那么以下说法正确的是: A.磁铁移近时受到圆环的斥力,离开时受到圆环的引力. B.磁铁移近和离开圆环两种情况下,圆环中感生电流方向不变. C.磁铁运动到圆环中心时,环中电流最大. D.磁铁运动到圆环中心时,环中电流为零. 该题的参考答案是A、D、笔者认为这个答案是错误的.
In the “High School Physics Comprehensive Test Question” published in the 3rd issue of this issue in 1992, there is such a question in multiple-choice questions: As shown in the figure, A is a fixed superconductor ring, and a piece of magnet is at the infinity from the right side The axis of the ring moves toward the ring and passes through to the left side at infinity. Then the following statement is true: A. The repulsive force of the ring is exerted when the magnet moves closer to the ring, and the ring is attracted when leaving the ring. B. Magnet moves closer and closer In the two cases of leaving the ring, the direction of the induced current in the ring does not change. C. When the magnet moves to the center of the ring, the current in the ring is maximum. D. When the magnet moves to the center of the ring, the current in the ring is zero. The answer to the question is A, D, and the author thinks this answer is wrong.