I'm in an elementary E&M physics class and thought I understood voltage and current pretty well until we got to resistance. I have a few questions concerning the effect of resistance on current that I hope somebody will be able to answer...I know I am missing something fundamental in my thought process. 1. How is a certain potential difference applied to/maintained in a resistor? Why doesn’t the potential difference change depending upon the current that is passing through it rather than the other way around? 2. I know that electrical energy is converted into thermal energy when passing through a resistor, thus leading into the reducing of the current through the resistor, but how does this make sense when the current leaving a resistor must be the same as the current entering a resistor? 3. How does one mathematically calculate the current in an ideal battery? Since you can’t use V=IR, is there any other way to do it besides using P=IV or any of the other more complex ways (such as in using drift velocity, number of charge carriers per volume, etc.)? Thanks to anyone who might be able to help clear up my questions.