所屬科目:教甄◆物理科專業
9. Figure 1 shows a wood cylinder of mass m = 0.25 kg and length L =0.10 m, with N = 10 turns of wire wrapped around it longitudinally, so that the plane of the wire coil contains the long central axis of the cylinder. The cylinder is released on a plane inclined at an angle 6 to the horizontal, with the plane of the coil parallel to the incline plane. If there is a vertical uniform magnetic field of magnitude B = 0.50 T, what is the least current I through the coil that keeps the cylinder from rolling down the plane?
12. One hundred turns of (insulated) copper wire are wrapped around a wooden cylindrical core of cross-sectional area 1.20x10-3 m2. The two ends of the wire are connected to a resistor. The total resistance in the circuit is 12.0 . If an externally applied uniform longitudinal magnetic field in the core changes from 1.60 T in one direction to 1.60 T in the opposite direction, how much charge flows through a point in the circuit during the change?
3.如右圖,在平面平行板上坐標x = 0的 A點,有一束窄光垂直射到板上,板 材料的折射率按公式變化, 式中n0和R為定值。光束在B點與原 方向成(X角離開平行板,試求B點的 x 坐標? (5%)
4.如右圖所示,厚度s、半徑R、質I m的金屬圓板,在平行地面 之均勻磁場5中落下,若金屬圓板維持鉛直下落,使圓板面平 行磁極且垂直地面,假設比R小很多,重力加速度以g表示。 試求金屬圓板下落的加速度?(5%)