the last successful invasion of Britain was by
A. the Spanish Armada
B. the Nazis
C. the Normans
D. the Americans
查看答案
Three of these statements are real reasons why the British Empire was successul. One of the statements is FALSE. Choose the FALSE one.
A. Britain was protected from frequent wars because it was on an island.
Britain was successful because it was the first European country to begin an empire.
C. Britain was successful because it emphasized trade relations with its colonies.
D. Britain was successful because it had an excellent navy.
测量三相交流电路的功率有很多方法，其中三表法适用于测量( )电路的功率。
A. 三相三线制
B. 对称三相三线制
C. 三相四线制
测量三相交流电路的功率有很多方法，其中二表法是测量( )电路功率的方法。
A. 三相三线制
B. 对称三相三线制
C. 三相四线制
已知容抗Xc=6Ω的对称纯电容负载作Δ接，与对称三相电源相接后测得各线电流均为10A，则三相电路的视在功率为（ ）
A. 1800VA
B. 600VA
C. 600W
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