Resistor & power dissipated question--please help 1. The problem statement, all variables and given/known data Load resistor R is attached to a battery with EMF E and internal resistance r. For what value of the resistance R in terms of E and r will the power dissipated by the load resistor be a maximum? 2. Relevant equations 3. The attempt at a solution So, first utilizing Kirchoff's Loop Law: E-Ir-IR = 0 E - I(r+R) = 0 I(r+R) = E r + R = E/I R= E/I - r the answer is r, but I'm not understanding why the resistor has to have a maximum value, or how to get r.