試題詳解

(15)A capacitor is placed between the poles of a large magnet, as shown in the right figure. In the space between the plates of the capacitor, there is a uniform electric field E and also a uniform magnetic field B; the two fields are parallel and in the direction of Z. A small sphere, carrying charge q = 6 μC, has an instantaneous velocity u = (6 × 10⁴)(0.766î + 0.643k) m/s. If d = 50 cm, V = 3000 V, and B = 2.0 T, what is the instantaneous force on the sphere?
(A)0.552î + 0.018k N
(B)0.643î + 0.036k N
(C)0.766î + 0.036k N
(D)0.766î + 0.643k N
(E)0.552î + 0.036k N