题干

小林家买了一台“220V 1500W”的热水器,由于安装的位置离固定插座太远,便到商店买了标有“220V 6A”字样的插座、标有“220V 10A”字样的两脚插头以及导线,组装了一个多孔的移动插座(如图所示).这个移动插座存在的两个问题:①____;②____.

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答案(点此获取答案解析)

插座允许通过的电流小于热水器正常工作时的电流,从安全用电来说,两脚插头没有接地线

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    Jonathan Cranwell sat on a hard bench behind the long narrow desk and watched the flies fly lazily in the sun. The drone of the younger boys reading letters and the older boys reciting Latin verbs made him sleepy. Jonathan had to force his eyes to stay open. He wanted to learn something new!

    He looked up at the schoolmaster's high desk in the front of the room. The new teacher was from Harvard College. Jonathan's father had been impressed with him. The boys had already had several other teachers, but none of them seemed to inspire Jonathan. So far, there was nothing to show that this one was special , though he'd only been there two days.

    “It's too hot to sit and memorize lessons,” the schoolmaster said. “We'll move outdoors for the next part of our lesson.” He led the group of boys into the schoolyard. “You younger boys, dig for grubs and beetles ( 幼虫和甲虫). Count their feet. See if you can describe their shells”

    Jonathan watched the teacher surrounded by laughing young students. No one had ever used the schoolyard itself for a classroom. “What next ?” he thought. He didn't have time to think about the younger boys, for he was running after butterflies and dragonflies himself.

    Jonathan and his friends liked this new way of learning.

    “It will be a clear night tonight. Go outside and look at the sky,” said the schoolmaster. “Look at the stars and notice their brightness and the patterns they make. These patterns have names from Greek mythology(神话), names like Orion, Aries, and others. Tomorrow we will learn about the ancient stories on them.”

    “How is the new schoolmaster ?” asked Jonathan's father that evening, when Jonathan announced he was going out to look at the sky.

    “He's different from any other schoolmaster we've had,” Jonathan admitted. “He seems interested in everything around him, and he wants us to be curious too. He even used the schoolyard as a classroom!”

    “So Mr. John Adams and his new ways make school useful to you after all,” joked Jonathan's father.

    “I believe he has,” said Jonathan. “I know I won't forget the lessons he has taught us!”