将合适的短语依次填入下列5空:If you are standing1, there could be less2difference across you,3you could4be injured or even killed by current5 through your body.
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Electricity will only flow if it can travel in a.
A. current
B. circuit
C. circle
D. cycle
The power should be turnedbefore the globe is replaced.
A. out
B. on
C. in
D. off
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