| 如图所示，两根相距为l的平行直导轨ab、cd、b、d间连有一固定电阻R，导轨电阻可忽略不计；MN为放在ab和cd上的一导体杆，与ab垂直，其电阻也为R；整个装置处于匀强磁场中，磁感应强度的大小为B，磁场方向垂直于导轨所在平面（指向图中纸面内）；现对MN施力使它沿导轨方向以速度v（如图）做匀速运动；令U表示MN两端电压的大小，则（ ） A．U= B．U= C．U=vBl，流过固定电阻R的感应电流由b到d D．U=vBl，流过固定电阻R的感应电流由d到b  |
答案：A
Introduction Consisting of 10 main islands and eight smaller islets off the west coast of Africa, Cape Verde is an archipelago with a lot to offer tourists, whether they are looking for a relaxing beach holiday, great surfing or a hiking trip in valcanic and mountainous landscape. Sal, the main tourist island, has wonderful sandy beaches to rival any in the world and also fantastic surfing and diving spots. With its warm climate all year round, wonderfully dirverse landscapes, friendly locals and great food and music, Cape Verde really is an attractive destination. 1. With year round warmth and cold ocean currents helping to keep the temperatures from rising too high, Cape Verde has an attractive climate for torists, and the majority of visitors are Western Europeans. The people who go to Cape Verde for the beach life tend to be families, while it is quite a young, adventure- seeking crowed that goes there for the diving or surfing. 2. Cape Verde is located in the Atlantic Ocean some 500 km to the west of the Afican continent. Indeed, the name itself is taken from the name of that western－most tip, which can be found on Senegal. The islands are divided into two groups-the Barlavento (windward islands) and the Sotavento (leeward islands). 3. With warm sunny days year round there really is no bad time to go to Cape Verde.Some visitors might preder to visit in winter and spring when daytime temperatures are a couple of degrees cooler and rarely exceed 25 ? 4. The resorts on Sal have plenty of facilities for families and the beaches by Santa Maria are great for kids, with their white, fine sand. On some of the islands it is possible to do a bit of bird and turtle spotting without intruding too much on their habitats, and on Sao Vicente and Santiago it is possible to go horse riding. 5. On the islands public transport services are by minibuses or trucks. Taxis in central areas are cheap. Between the islands of Santiago, Sao Vicente and Sal there are flights at least once daily. Flights to the other islands are less frequent. TACV Cabo Verde Airlines (www.flytacv.com) is the main operator. There are regular ferry services between the islands, but departures are sometimes unpredictable. |
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