在地球赤道上空，沿东西方向水平放置一根通以由西向东的直线电流，则此导线受到的安培力方向
A．竖直向上
B．竖直向下
C．由南向北
D．由西向东
答案：A
题目分析：地球是一个大磁体，地球表面附近赤道上空地磁场呈水平方向，由南向北，其他地方的磁场方向均不言水平方向，水平分量南北半球均由南向北，竖直分量，北半球竖直向下，南半球竖直向上。安培力的方向由左手定则判断。
地球表面附近赤道上空地磁场呈水平方向，由南向北，电流方向由西向东，由左手定则可判断导线受到的安培力方向竖直向上所以，A选项正确，BCD选项错误
点评：中等难度，地磁场的南极、北极分别是地理的北极、南极，赤道上空地磁场呈水平方向，北半球竖有直向下分量，南半球竖有直向上分量，所以涉及地磁场问题一定首先搞清楚问题发生的地理位置。熟练应用左手定则
Do your spirits soar (猛增) on a sunny day? Do you relax at the sound of flowing water? Some scientists suggest that these contacts with nature are good for your health. In one study, hospital patients with a view of trees had shorter hospital stays and less need for pain medications. Another study indicated that prisoners with a view of the outdoors had fewer doctor visits. “Why do we desire nature? Maybe we’re programmed to need it, since our ancestors’ survival was so dependent on their connection with nature,” suggests biologist E.O. Wilson. Want to find out if contact with nature improves your outlook on life? Try a few of these ideas. Hang out a bird feeder and watch the birds that visit it. Sit down in the backyard or a nearby park. Close your eyes. What do you hear? Birds singing? The wind in the trees? Crickets (蟋蟀) chirping? Find an anthill. Sit down and watch the ants work. Take a walk right after a rainstorm. What looks different? Smells different? Go barefoot on a sandy beach. Open the curtains and the window, if the weather allows it. On a windy day, watch the trees. Go to a creek, river or park fountain. Listen to the sound of water in motion. Camp out in the backyard or at a nearby state park. Use a tent or sleep on the ground. Find a wide-open space to study the stars. Learn about the different constellations (星座). Raise a garden. Or plant some seeds in a flowerpot. Go hiking with your family. Talk about all of the colors you see in nature. Take a camera and capture your nature experience. 小题1:From Paragraph 2 we can learn that ______.
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