题目内容

The power should be turnedbefore the globe is replaced.

A. out
B. on
C. in
D. off

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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

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

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