题目

如图所示为电吹风的电路原理图。电动机M上标有“220V  100W”字样，电热丝的电阻R＝额定88Ω。求： ⑴闭合S1，断开S2，正常工作当送风8min，消耗的电能； ⑵闭合S1，S2，正常工作当送热风时，电路消耗的总功率。   答案：解：（1）                              3分 （2）  或           1分 （或）   1分                              1分In some parts of the United States, farming is easy. But farming has always been difficult in the northeastern corner of the country, which is called New England.New England has many trees and thin, rocky soil. Anyone who has wanted to start a new farm there has had to work very hard. The first job has been cutting down trees. The next job has been digging stumps (树桩) of the trees out of the soil. Then the farmer has had the difficult job of removing stones from his land.The work of removing stones never really ends, because every winter more stones appear. They come up through the thin soil from the rocks below. Farmers have to keep removing stones from the fields. Even today, farms which have been worked on for 200 years keep producing more stones.That is why stone walls are used instead of fences around New England fields. The stone walls are not high: A man can easily climb over them. But they keep the farmer’s cows from joining his neighbour’s cows.64.   New England is an area ______.in the northeastern part of Britain        which has been newly discovered by the Englishmen which lies between Australia and New Zealand which lies in the northeastern part of the USA65.   According to the passage, farming is difficult in New England because ______. A．the winter is very long there B．the farms are very old C．the soil is rocky and thin D．there are not enough machines for farming66.   From this passage, we know the removing of stones ______. must be done again and again             is usually done during the winteris an interesting job children enjoy doingwas more difficult before machines were used67.   In New England, stone walls are used to ______.keep dangerous beasts outkeep the farmer’s cows from wandering awayprotect the farmers fields from thievesprovide comfortable living conditions for the farmer’s family