如图所示，在电磁铁正上方用弹簧挂着一条形磁铁，开关闭合后，当滑片P从a端向b端滑动过程中，会出现的现象是

​

完形填空

    Yesterday evening，when l went to town with my  1  ，we met a strange old man．It was raining ham and we had no  2 ．We were trying to get into a taxi when he came up to us．He was 3  a nice umbrella and he said that he would give it to us for only a pound．He had forgotten his   4 ，he said，needed taxi—fares(出租汽车费)to go back home．My mother didn't believe  5 he had said at first，and asked him a lot of questions．Finally we bought it and he left  6 ．We followed him and found he went into a pub(小酒店)and  7  himself a glass of whiskey(威士忌)with the pound．

8 he drank it，he put 9   his hat and took up one of the many wet umbrellas at the entrance and went off．Soon after that，he sold it again．What a(n) 10  experience I had !

如图当我们做伸肘动作时，图中的①和②所处状态分别是（   ）