题目

阅读下面材料, 根据其内容和所给段落开头语续写两段, 使之构成一篇完整的短文。Long ago, there was a big apple tree. A littleboy loved to come and play around it every day. He climbed to the top of the tree,ate the apples, and took a nap under the shadow. He loved the tree and the treealso enjoyed playing with him. As time went by, the little boy grew up and heno longer played around the tree. One day, the boy came back to the tree, appearingsad. Come and play with me, the tree asked the boy gently. I am no longer a kid; I won't play around trees anymore, thebo如图所示电路中，RL=6 Ω，电流表的量程为0 ～0.6A ，电压表的量程为0 ～3V ，电源电压为8V 。为了使两表都能安全使用，对变阻器连入电路的阻值有何要求？