2. An external resistor with resistance R is connected to a battery that has emf & and internal resistance r. Let P be the electrical power output of the battery. By conservation of energy, P is equal to the power delivered to the external resistor. r ww R E (a) Find P in terms of E, r, and R. (b) If & = 40 V and r = 2 02, calculate the power delivered to the external resistor for six different values of R: 0.25 , 1 , 1.75 , 2.5 , 3.25 , and 4. (c) In Part (b), you should have found that P does not increase monotonically as R increases. Using the equation for P from Part (a), find the value of R in terms of r such that P is maximized. What is the maximum value of P in terms of & and r?