故 乡 的 云

    有人喜欢皎洁的明月，有人喜欢壮观的瀑布，有人喜欢夜晚的星空，有人喜欢淡淡的晚霞。而我却喜欢那变化多端的云。

    故乡的云十分美丽。有时薄得像一层纱，有时厚得像一床被；有时分散成一块一块的，有时聚集成一座座小山。故乡的云又十分可爱。时而像一只小白兔，一蹦一跳，像和谁赛跑似的；时而像一只大黑象，鼻子里都是水，“哗啦，哗啦”地往下洒；时而像一只猫，正在睡懒觉，对外面的事情漠不关心。有时云儿们又会聚到一起，像是在说悄悄话。

    故乡的云变化多端，我最爱故乡的云。  

   It is 1965，a 1ittle boy is on the beach (海滩) with his parents. He is four years old. The boy plays near the water. He walks into the water. His parents aren’t watching him．
   The water is over the boy’s head! A woman sees the boy. She picks up the boy and carries him to his parents. The woman’s name is Mrs Blaise．
   It is 1975,ten years 1ater.The boy is on the same beach. He is 14 years old now. He is big and strong. He is a good swimmer. A man is in the water. The man can’t swim. ‘Help! Help!’ the man cries．
   The boy runs into the water. He swims to the man and pulls the man to the beach. ‘Thank you. Thank you.’ says the man. Who is the man? His name is Mr Blaise. He is Mrs Blaise’s husband．

问题：并联电路干路电流与各支路电流有什么关系？

猜想：干路中的电流等于各支路中的电流之和．

设计实验：略

进行实验：如图连接电路，闭合开关，记录A、B、C各点的电流值如下表所示