题目

Learning about the environment is very important. There are many good books that will help you learn. To get started, ask your teacher or a librarian for some suggestions. You can also look at some good websites with information about the environment and climate (气候) change. Climate change may be a big problem, but there are many little things we can do to make a difference.Driving a car or using electricity is not wrong. We just have to be smart about it. Some people use less energy by carpooling. For example, four people can ride together in one car instead of driving four cars to work. 硅光电池是一种可将光能转化为电能的器件，已经得到广泛的应用，某同学设计如图所示的电路探究硅光电池的路端电压U与总电流I的关系。已知硅光电池的电动势大约是5V, 电压表的量程只有0—3V,内阻为5k ，定值电阻R0=5k ,电流表可视为理想电流表。（1）用一定强度的光照射硅光电池，调节滑动变阻器，得到电压表的读数U与电流表的读数I的关系图线，如图乙所示，可知电池内阻__________（填“是”或“不是”）常数，短路电流为____________mA, 电动势为________V（保留三位有效数字）（2）若将R=20 k 的电阻接在该硅光电池的两极上，则该电阻消耗的功率为________mW,此时该硅光电池的内阻为______________k 。（保留三位有效数字）