题干

小闵同学在做“用电流表、电压表测电阻”的实验中,选用了若干节新的干电池作为电源,标有“20欧 1安”字样的滑动变阻器及其它相关器材.他先用导线把待测电阻、滑动变阻器、电流表、电源、电键串联连接,再把电压表并联接入电路中.实验中,小闵根据需要改变了电表量程,但没改变各电表接入的位置.在保持电路安全的情况下小闵移动滑片,他记录下了电压表的最大示数为6伏,最小示数为2.6伏;且观察到电压表的示数从6伏变化到4.5伏时电流表示数的变化量为0.29安.
上一题 下一题 0.0难度 选择题 更新时间:2019-03-07 11:18:22

答案(点此获取答案解析)

同类题2

阅读理解

    Imagine waking up one day and finding that your beautiful local beach is no more—gone, its fine white sand swept away by an abnormal storm. You go about your daily business for 12 long years and then suddenly the beach is back, all its glory restored by another storm. This is what happened on the island of Achill, off the coast of Ireland, where people are celebrating the return of the beautiful Ashleam Bay beach that was taken from them in 2005.

    That in itself is unusual enough, but the story gets even better! You see, another beach in Achill did a disappearing act once, but took much longer to return. The beach at Doonagh, located only six miles away from Ashleam Bay, was restored earlier in 2016 after waves created by spring storms had swept away all the sand in 1984, leaving just rock pools behind.

    There is local legend that stretches back hundreds of years that says this beach at Ashlcam Bay returns for a short every seven years then disappears again. But this time around it took a bit longer than that. It was last seen in 2005 and it stayed for a few months at that time before it was washed away again.

    As you can imagine, everyone on the island of Achill is thrilled to have their sandy beach back, and even though no one knows how long it's going to be around for, they are making the most of the time they've got before it disappears again.

    Some may be quick to believe climate changes cause the phenomenon, but that's not the reason these two beaches in Achill keep disappearing, Dr Kevin Lynch, a geographer at NUT Galway, says that these occurrences are the result of hydrodynamics (流体力学) and sediment(沉积物) supply, rather than climate changes.

    Regardless of what's causing them, disappearing and reappearing beaches are just part of what makes nature so fascinating.