3A的直流电通过电阻R时,t时间内产生的热量为Q;现让一交流电通过电阻R,若2t

题型:选择题

问题:

3A的直流电通过电阻R时,t时间内产生的热量为Q;现让一交流电通过电阻R,若2t时间内产生的热量为Q,则该交流电流的有效值和最大值分别为(  )

A.I=3/2A,Im=3A

B.I有=3A,I=3A

C.I有= A,I A

D.I3A,Im=6A

考点:交变电流的周期和频率
题型:选择题

在匀强电场中,将一电荷量为2×10-5C的正电荷由B点移到A点,电势能增加了0.2J,已知A、B两点间距=2cm,两点连线与电场方向成60°角,如图所示,问:

(1)A、B两点间的电势差为多少?

(2)该匀强电场的电场强度为多大?

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口腔修复工艺焊接技术中,常用的白合金焊料熔化温度()。

A.350~450℃

B.500~600℃

C.650~750℃

D.800~850℃

E.950~1050℃

题型:选择题

商业贿赂与附赠的区别?

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Since we are social beings, the quality of our lives depends in large measure on our interpersonal relationships. One strength of the human conditions is our possibility to give and receive support from one another under stressful conditions. Social support makes up of the exchange of resources among people based on their interpersonal ties. Those of us with p support systems appear better able to deal with major life changes and daily problems. People with p social ties live longer and have better health than those without such ties. Studies over types of illnesses, from depression to heart disease, show that the presence of social support helps people defend themselves against illness, and the absence of such support makes poor health more likely.
Social support cushions stress in a number of ways. Firstly, friends, relatives and co-workers may let us know that they value us. Our self-respect is strengthened when we feel accepted by others in spite of our faults and difficulties. Secondly, other people often provide us with informational support. They help us to define and understand our problems and find solutions to them. Thirdly, we typically find social companionship supportive. Taking part in free-time activities with others helps us to meet our social needs while at the same time distracting us from our worries and troubles. Finally, other people may give us instrumental support—money aid, material resources, and needed services—that reduces stress by helping us resolve and deal with our problems.

Which of the following is closest in meaning to the underlined word "cushions"

A. takes place of


B. makes up of
C. lessens the effect of

D. gets rid of

题型:选择题

大处理量下装置生产中可能出现的难点有()。

A.焦炭塔焦层较高

B.分馏塔底结焦

C.加热炉炉膛温度超

D.原料泵超电流

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