【简答题】
如图所示,一根长为L的金属细杆ab绕竖直轴O<sub>1</sub>O<sub>2</sub>以角速度ω在水平面内旋转,O<sub>1</sub>O<sub>2</sub>在离细杆a端/5L处,若已知地磁场在竖直方向的分量为<img src="https://nimg.ppkao.com/2019-05/wangjing/2019050917270237104.jpg?sign=ee594f368381b0b641175e8dbf953003&t=62d6feab" />。求ab两端间的电势差V<sub>a</sub>—V<sub>b</sub>。<br /> <img src="https://nimg.ppkao.com/2019-05/wangjing/2019050917271063501.jpg?sign=7bd5ffd90fdcdcd94656452fc84b5bb1&t=62d6feab" />