对频繁、重载起动的电动机,其过负荷保护可选用()。
A、热继电器
B、熔断器
C、过电流延时继电器
D、断路器
参考答案:C
On hearing of the case some time later, Conan Doyle was convinced that the man was not guilty, and immediately went to work to ascertain the truth.
A. explore B. obtain C. verify D. search
一物体从A点到达B点作匀变速直线运动,若在A、B中点的速度为v1,在这过程中间时刻的速度为v2,则()。
A.作匀加速运动时,v1>v2
B.作匀减速运动时,v1>v2
C.作匀加速运动时,v1<v2
D.作匀减速运动时,v1<v2