I'm a TA for a sophmore level E&M lab course that is taught independent of the lecture. So most of my students are seeing these concepts for the first time in the lab setting (learning through discovery). Many of them are having problems visualizing the concepts of the voltage, current and resistance. However, most of them have had mechanics, so they understand the concepts of potential energy and work. I understand the fundamentals of E&M, but I'm having a hard time describing it in ways that the students can grasp and internalize. I've managed to make some promising headway by making the parallel between electrical potential and gravitational potential and relating that back to voltage, but am not sure how (or if it's worthwhile) extending that metaphor further. So, can anyone have a solid, basic description of voltage, current and resistance that would make sense to someone who has had basic mechanics?