18. A charged particle (m = 2.0 g, q = -50 μC) moves in a region of uniform field along a helical path (radius = 4.0 cm, pitch = 8.0 cm) as shown. What is the angle between the velocity of the particle and the magnetic field?
(A)27°
(B)72°
(C)63°
(D)18°
(E)58°
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統計: 尚無統計資料
統計: 尚無統計資料