43. The figure shows a 2.0-cm diameter roller that turns at 90 rpm. A 4.0-cm wide plastic film is being wrapped onto the roller, and this plastic carries an excess electric charge having a uniform surface charge density of 5.0 nC/cm2. What is the current of the moving film?

(A) 190 nA
(B) 23 μA
(C) 30 nA
(D) 11  μA
(E) 16 nA.

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統計: A(7), B(1), C(0), D(0), E(0) #3093884

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