题干

用下列器材测量电容器的电容:

一块多用电表,一台直流稳压电源,一个待测电容器(额定电压16V),定值电阻R1(阻值未知),定值电阻R2=150Ω,电流传感器、数据采集器和计算机,单刀双掷开关S,导线若干.

实验过程如下:

实验次数

实验步骤

第1次

①用多用电表的“×10”挡测量电阻R1,指针偏转如图甲所示.

②将电阻R1等器材按照图乙正确连接电路,将开关S与1端连接,电源向电容器充电.

③将开关S掷向2端,测得电流随时间变化的i﹣t曲线如图丙中的实线a所示.

第2次

④用电阻R2替换R1,重复上述实验步骤②③,测得电流随时间变化的i﹣t曲线如图丁中的某条虚线所示.

说明:两次实验中电源输出的直流电压恒定且相同.

请完成下列问题:

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    Climbers at Qomolangma are being asked to clean up after themselves.

Qomolangma has earned the nickname(绰号)the World's Highest Garbage Dump(垃圾场).

    Climbing Qomolangma,the world's highest mountain,just becomes more challenging.The government of Nepal is telling climbers they cannot leave trash on the trails.Each climber will have to come down the mountain with at the least 18 pounds of garbage.That's the average amount of trash a climber leaves behind on Qomolangma.

    Officials say climbers are responsible for their own trash.“We are not asking climbers to pick up trash left by someone else,”said the Nepal Tourism Ministry.“We just want them to bring back what they took up.”

    More than 4,000 people have reached the 29,035-foot summit(顶峰)in more than 60 years.Leaving trash along the way helps climbers keep their bags light so they have energy to reach the summit.“The trash problem in Qomolangma is not new.”Burlakoti says.“When the people started to climb the mountain,they started to leave their garbage there.”They have left behind bottles,food boxes and equipment.

    The new rule came into effect in April,2014.To make sure it is followed,climbers will have to deposit money(交保证金)before they climb.Once they climb back down the mountain,officials will check climbers at a return camp to make sure they have the required 18 pounds of trash.If they do,their money will be returned to them.If they do not,climbers will not receive their deposit and they will not be given a permit the next time they want to climb Qomolangma.

    The goal is to make sure no more litter will be left on Qomolangma."As we offer Qomolangma to all the people of the world they should take responsibility to clean it."Burlakoti says,“After seeing the results from this,we will also apply this rule to other mountains.”