题干

电动轮椅为残障人士出行提供了方便.某型号的电动轮椅质量为20kg,轮子与地面的总接触面积为20cm2.其工作原理如图所示,操纵杆可以同时控制S1和S2两个开关。向前推操纵杆时轮椅前进且能调速,向后拉操纵杆时轮椅以恒定速度后退.已知蓄电池电压为24V,定值电阻R2=20Ω,R1为滑动变阻器。分别将S1和S2同时接触对应点____(选填“1”或“2”)时,轮椅前进;当轮椅后退时,电流表示数____(选填“大于”、“小于”或“等于”)1.2A。


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1,小于

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    How much and how well you sleep will likely change. Most people start needing reading glasses around forty, and many have some hearing loss later in life. Starting in your fifties, bone aging increase. How you feel as you get older depends on many things, including what health problems run in your family and the choices you make.

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    What do you need to do to feel your best as you age? One of the most important things you can do for your health at any age is to be physically active. Physical activity keeps your body strong, and it helps with how you feel. People who stay active are less likely to get depressed.

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