Solve

Method 1: Progressive \"collapsing\" of circuit elements In last week's discussion, we learned how to analyse circuits involving batteries and capacitors. Our method was to progressively collapse groups of capacitors (connected in series or in parallel) into effective capacitors. Once the circuit became simple enough, we could calculate everything about it: charge and voltage. Then we worked backwards, breaking up each combination and calculating the charge and voltage on the individual capacitors. This week, we will analyze circuits involving resistors. As you know, the formulas for combining resitors in series and in parallel are \"opposite\" to those for capacitors. We also need an expanded set of rules for \"breaking up\" combinations of devices: e For devices connected in parallel: the voltage across them is always the same. e For devices connected in series: the charge and current is always the same. But otherwise, the procedure is the same! (a) Can you explain the rules stated above in terms of physical principles? They have simple physical origins, so they're easy to remember. (b) Consider the circuit shown at right. All the resistors Rj have the same value R. Find the current I4 through resistor Rg (including its direction) and the electric potential Va at the indicated point A. Be sure to express your answers in terms of the given parameters (battery \"EMF\" = voltage) and R (resistance of each resistor)