题干

某同学将一直流电源的总功率PE、输出功率PR和电源内部的发热功率Pr随电流I变化的图线画在同一坐标系中,如图中的a、b、c所示.则下列说法中正确的是(   )

A:图线b表示输出功率PR随电流I变化的关系

B:图中a线最高点对应的功率为最大输出功率

C:在a、b、c三条图线上分别取横坐标相同的A,B,C 三点,三点的纵坐标一定满足关系PA=PB+PC

D:两个图线交点M与N的横坐标之比一定为1:2,纵坐标之比一定为1:3

上一题 下一题 0.0难度 选择题 更新时间:2019-05-11 03:09:26

答案(点此获取答案解析)

C

同类题2

阅读下列短文,从每题所给的四个选项(A、B、C和D)中,选出最佳选项。

     Joe is interested in getting exercise and competing (竞争) on a team. He reads about the events at the local pools and finds the perfect activity.

                                                                           Swimming Programs

     Summer Swim Team

     Join a Summer Swim Team and compete with other swimmers! The program is offered at eight different local pools for youths to 17 years old. The season runs June 21-August 21. Practices are daily (Monday through Friday) throughout the summer. Cost: $50.00.

Buckman

2-3 P.M.  

      Montavilla

8-9 A.M.

Creston

7-9 A.M.   

      Peninsula

4-7 P.M.

Dishman

8-9 A.M.

      Pier 

noon-1 P.M.

Grant

8-10 A.M.    

      Sellwood

7-9 A.M.

     Junior Swim Instructor (少年游泳教练)

     Two weeks, 20 hours of instruction, two hours per day for children 11-14 years old. Pre-training for youths interested in becoming swim instructors ($45 per child).

     Junior Lifeguard (救生员)

     Two weeks, 30 hours of instruction, three hours per day for children 11-14 years old. Pre-training in lifeguarding, and customer (消费者) service ($45 per child).

     Junior Swim Instructor & Junior Lifeguard Training Dates

June 28-July 9

August 9- August 20

June 12-July 23

August 23- September 3

June 26-August 6


     Special Offer

     Anyone who takes part in both junior swim instructor and junior lifeguard programs at the same time need only spend $75 instead of $90 for 50 hours of training.

     Register(注册) Online

     You can now register online! Visit our website at http://www.example.com. You can choose an area of town, a specific local center, a program, or search for classes which can meet the needs of students of different ages. Just visit our website, and you're on your way!