Hi guys, i need some help here... 1. I know that by convention, the positive charge of the voltage source is taken to be the direction of current, but I'm confused by this MIT lecture vid that drew the current as appearing to be flowing from the negative terminal. You can see the drawing in the video here: http://youtu.be/RsJ1eg7XNVs?t=10m5s and I have specified the timing in the link already. So why is this the case? Is that just a reference current? Meaning if we use kirchoff loop or junction rule, the direction actually doesn't matter as it's just your own personal preference. But while this is tempting to do, why is the current drawn as if the reference current is the real current? 2. For Kirchoff's Loop rule, we let sum of voltages in a loop V1+V2+V3=0 right? V2 and V3 can be expressed as IR where I is the current flowing through it and R the resistance of the component. Let's say we start from a particular voltage source of V1. If that's the case, when we use the loop rule starting from this voltage source of V1, V1 must first be positive right? 3. Lastly, what if there is two voltage sources in the circuit (DC for example), do we always take the highest voltage source and the smaller one as a component (like a resistor) only? Does the current actually "cancels" out each other if they flow in opposite direction? If these 2 sources have currents that "collide" at a junction, which is the direction of the current that actually flows? Thanks a lot for your help!