在金属导体中 ,电流跟电压成正比 ,伏安特性曲线是通过坐标原点的直线 ,具有这种伏安特性的电学元件叫做线性元件。-In metal conductors, the current with the voltage proportional to the volt-ampere characteristic curve is a straight line through the origin, with the volt-ampere characteristic of this electri