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    What's the red star in the sky through a telescope(望远镜)? It is Mars. Do you want to know more about it? Take the “Mars Orbit Express”!
  “Mars Orbit Express” is a space probe (探测器). It was sent towards Mars by American scientists on August 12th, 2005. Its tasks are to study Mars' atmosphere and return photos to Earth. But before that “Mars Orbit Express” must travel about 100 hundred million kilometers and seven months. It reached Mars' orbit(轨道)in March, 2006.
    Mars and Earth have similar weight and size. However, Mars is closer to the sun than Earth. Mars is very cold. The average temperature is below 50℃. The temperature at noon only reaches 20℃ during a Mars day. Its atmosphere is mostly CO2. It has much sand and two moons---Phobos and Deimos.
    Scientists think Earth and Mars had similar beginnings 4.6 billion years ago. But while Earth supports millions of lives,Mars becomes bad. “Earth easily could have turned out like that.” said an scientist, “It is important for us to find out why and Mars Orbit Express' should do that.” “Mars Orbit Express” also would help scientists to learn what might happen to Earth in the future.  “Mars Orbit Express” would work for about four years.

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如图所示是某电热器的工作原理图,R1、R2是发热电阻,虚线框为电热器的金属外壳。它用一个旋转开关可以实现电热器多档位工作的要求。其中旋转开关内有一块绝缘圆盘,在圆盘的左边缘依次有4个金属触点①、②、③、④,右边缘是一金属板,可绕中心轴转动的开关旋钮两端各有一个金属滑片,转动开关旋钮可以将左边缘相邻的两个触点与右边缘的金属板同时连通。如旋到图中位置S时,金属滑片将1、2两触点同时与右边缘金属板接通。

导    线    规    格
导线横截面积S/mm20.511.52.5
安全载流量I/ A481220

(1)如果请你为这台电热器配备一个三脚插头,如图乙所示,应该将电路图中的地线接到插头的____ (选填“G”、“L”或“N”)脚。正常情况下,火线和零线之间的电压为____ V。
(2)小明想在电路中加一个“倾倒开关”,使电热器被碰倒时能自动断开电路,以免引起火灾。该开关最好应安装在示意图中A、B、C、D、E中的____ 点处。
(3)如果 R1=R2,旋钮开关旋到位置S时的电功率为1000W,求R1和R2的阻值。____ 
(4)当旋钮开关旋到位置T时,通电1 min产生的热量是多少? ____ 
(5)某种橡皮绝缘铜芯导线在常温下安全载流量(长时间通电时的最大安全电流)如下表,请你计算说明应选横截面积为多大的铜芯导线作为该电热器的输出导线,才符合既适用又经济的原则?  ____