题目内容

A charged particle is released from rest in a region where there is a constant electric field and a constant magnetic field. If the two fields are parallel to each other, the path of the particle is a ().

A. circle
B. parabola
C. helix
D. cycloid
E. straight line

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Four equal-magnitude point charges, two positive and two negative, are arranged at the corners of a square. Let V and E be the potential and the electric field magnitude, respectively, at the center of the square, and let V0 and E0 be the same quantities at the same point if the upper left positive charge only were present. Which of the following expresses the values of V and E?

A. V = V0, E = E0
B. V = 4 V0, E = 0
C. V = 0, E = 4 E0
D. V = 4 V0, E = 4 E0
E. V = 0, E = 0

Even though the linesmen are touching a liveline, no circuit is formed, so they are not in danger.

A. energy
B. source
C. power
D. work

片重差异检查时,所取片数( )片

A. 10
B. 20
C. 15
D. 30

压片时出现松片现象,下列哪个做法不恰当( )

A. 选粘性较强的粘合剂
B. 颗粒含水量控制适中
C. 减少压片机压力
D. 调慢压片车速

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