___________ the guide, the reporter entered the house of the farmer who is famous for
helping other villagers get rich.
某静电场的电场线分布如图所示,图中P、Q两点的电场强度的大小分别为EP和EQ,电势分别为UP和UQ,则( )
下列四幅图中能说明电动机工作原理的是( )