You don't need to know much about circuits for the MCAT. You are likely to get a couple discrete questions that require you to know how current runs through resistors in series vs parallel, and its pretty easy to develop an intuitive understanding of this without understanding any complicated math at all. Sure, you can always go deeper, but the MCAT doesn't require that, and if you learn more than you need to when studying for the MCAT, your wasting precious time. Of course, if you are interested in physics and are curious, then you should definitely go for the calc based stuff, but I wasn't.